# Deepanshu's Message Board

Hi, everyone ! I'am Deepanshu gupta , Currently I'am Preparing For JEE 2015 ! In free time i also love to play football . I Join The brilliant.org in June 2014 , after joining this amazing site , my problem solving skill's get increased . Thanks to staff Member's for creating such Beautiful website . Also here i make some good friend's , and learn lot from teacher's . This is really Brilliant Site !

This is my message Board , you can leave messages for me here . Feel free to report , complain , suggestion for brilliant.org , I'am also an Moderator , So You are welcome to talk to me . !$\ddot\smile$

Thank You !

DEEPANSHU GUPTA

###### Note:

This note is going heavier , and loading very slowly ,So I will deleting comment's which are irrelevant and answered now . So that I can easily reach to you.

Note by Deepanshu Gupta
5 years, 4 months ago

This discussion board is a place to discuss our Daily Challenges and the math and science related to those challenges. Explanations are more than just a solution — they should explain the steps and thinking strategies that you used to obtain the solution. Comments should further the discussion of math and science.

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Could ypu send a link of all the brainstormers that are there ?

- 3 years, 1 month ago

hi deepanshu.....i'm pranav....exited to know. how much did u scored in mains and advanced also

- 5 years, 1 month ago

Hi deepanshu, I am unable to reply to your report(bug in the app) so I am writing it here(not everything)

• Assuming point mass won't help( V = 0 $\therefore$ B = 0) I have mentioned it to be cubical(for solving this problem don't focus on the shape) ,

• After coming at top it will eventually come down(density of block is more :D)

I hope this is sufficient for you to retry the problem :)

- 5 years, 3 months ago

No no , Actually I mean't that point size means to neglect his dimension's or not .... Okay evrything's clears now , Sorry That Time really messed up , I'am sorry for that ! Thanks

- 5 years, 3 months ago

Hi deepanshu, Can u please mark these disputes over here as resolved.

- 5 years, 3 months ago

Bro , actually we moderators are not allowed to marked report as resolved . But okay I can delete the reports , So I will delete the report , if once he is satisfied with his mistake ... does he ...?

- 5 years, 3 months ago

Hi buddy , can you please upload solution to this question : Interference in YDSE

- 5 years, 3 months ago

Sorry bhai , time ki shortage hai , I will upload after my mains , till then I can gave you hints on that question Post. You can tag others people for help , if they can .

- 5 years, 3 months ago

Hey, bro I have a doubt in a question. I have solved it but a concept needs to be cleared. Please see the problem "Rolling down Rolling down ...." . May be I am not getting the thing to be clear but whatever may be the reason please see the discussion carried in that problem, I have put forth my doubt. Please reply as soon as possible. Thanks in advance. And yeah ALL THE BEST for JEE, I would also be giving JEE in 2016.

- 5 years, 3 months ago

I think this Problem needs correct diagram , and I guess author of problem (Vraj) and problem solver confuse in diagram . See This

- 5 years, 3 months ago

Okay i get your doubt. $\text{Case 1:(releasing cylinder)}$ ![]( When we released the cylinder on the inclined the Point A on cylinder moves backwards wrt to B.Hence friction will act down the incline (opp to spin) on the cylinder decreasing it angular velocity.

$\text{Case 2:(Puer rolling)}$

When this angular velocity is enough for pure rolling then friction will act upwards as usual.

For more insight try to right eq of translatory motion of COM of cylinder in $1^{st}$ case.Hope this clears your doubt.

- 5 years, 3 months ago

Hi , Thanks for wishes , okay I'am trying that problem If I got correct then I will report back you! But Can you Please tell cylinder is solid or hollow ? I guess it should be solid , am i right ?

- 5 years, 3 months ago

Yeah its solid as nothing is mentioned

- 5 years, 3 months ago

- 5 years, 3 months ago

Please can you join the conversation in that question. I also have same doubt as Aditya Tiwari.

- 5 years, 3 months ago

Sorry i was not able to reply you soon but now i'll tell you, I am getting a bit confused. Can you please explain what happens after we have lowered down the cylinder. I did this question by assuming this concept that immediately we lower down the cylinder it will spin but will not move and for some value of friction it will pure roll but when i saw in the solution he took the final angular velocity to be zero after which it will pure roll.But for that the direction of friction should be down the incline but initially i took it up the incline. SO HOW THIS IS POSSIBLE !!!! Please Help !!!!

- 5 years, 3 months ago

Okay i get your doubt. $\text{Case 1:(releasing cylinder)}$ When we released the cylinder on the inclined the Point A on cylinder moves backwards wrt to B.Hence friction will act down the incline (opp to spin) on the cylinder decreasing it angular velocity.

$\text{Case 2:(Puer rolling)}$

When this angular velocity is enough for pure rolling then friction will act upwards as usual.

For more insight try to right eq of translatory motion of COM of cylinder in $1^{st}$ case.Hope this clears your doubt.

- 5 years, 3 months ago

Well then according to this question, we have to consider CASE 1. And considering it the force of friction is acting down the incline and net force acting on the sphere cannot be 0. It will be gravity + friction. And therefore the cylinder must move some distance down the incline before starting pure rolling.

- 5 years, 3 months ago

Hey all the things are getting little messed up. Will you please tell me how to post an image on a note !!!!! Please Reply.

- 5 years, 3 months ago

Hi

Actually I haven't yet solved the question yet , but the OP is my friend , so if you could write your doubt here , I'll call him immediately and resolve your doubt .

That is if your doubt is important for you !

- 5 years, 3 months ago

I can't believe I wasn't able to solve this.
A person picked up 13 cards from 52 cards. Find Probability that he has no ace , Probability that he has exactly one ace ?
Please solve this $\ddot\smile$

- 5 years, 3 months ago

Bro can you help me with this. thanks

- 5 years, 3 months ago

Let me give a try , If I got then i will report you.

- 5 years, 3 months ago

Okay. Thanks

- 5 years, 3 months ago

Check tis out!

- 5 years, 4 months ago

Could you help me out ? here

- 5 years, 4 months ago

@Deepanshu Gupta Please suggest me a good reference book for ray optics.

- 5 years, 4 months ago

I want to ask, how many of you use Physics Galaxy by Ashish Arora as a reference for Physics?

- 5 years, 4 months ago

Dude , that books good , but be warned , it has a lot of theory ! If you are willing to be industrious , go for it :)

- 5 years, 4 months ago

Sorry Brother I did not know indiidual source for ray optics. But I think H.cv has some good problems of ray optics . And No currently I did not have that galaxy's , But what was that physics galaxy in actual ? I really did not know about them . are they are study material for advance ? or anything else. @Ninad Akolekar

- 5 years, 4 months ago

@Deepanshu Gupta Physics Galaxy is a book for IIT JEE preparation. One of my physics faculty suggested me that. I feel that it as an awesome book. A wide coverage of theory, in detail with illustrative examples.

Not only this, it has good level of problems (much higher than DC Pandey, I feel) and not few, but many such problems. It has five types of problems- i. Practice Exercise (In-chapter exercise), ii. Discussion Questions (Theory/Reasoning type questions), iii. Conceptual Objectives, iv. Numerical Objectives and the best ones v. Numerical Subjective.

I like this book personally. It has so large number of problems that it becomes difficult to complete even a single chapter. You need to have a lot of patience and time, as well. Or one may attempt only the conceptual objectives and numerical objectives for JEE Main purpose/ Numerical Subjective for JEE Advance.

But there's a way out. Ashish Arora's website: Go and check out the advanced illustrations and download all mechanics brainstormers (tests), atleast.

Physics Galaxy Brainstormers

Okay, that was my personal point of view. One may have a different opinion. You can take suggestion from your faculties but I feel that you'll like the above mentioned Brainstormers, so I mentioned it. @Deepanshu Gupta

- 5 years, 4 months ago

Thanks !

- 5 years, 4 months ago

He could try Ray optics by DC Pandey.

- 5 years, 4 months ago

How much did you get in your boards (PCM %). I just finished with my boards and Iam expecting to get $85\quad$% in PCM. So I just wanted to know how much should I score in JEE at least to get a nice NIT.(general category)

- 5 years, 4 months ago

In which board r u ? I mean CBSE 12th board exams are running . And actually I Pass CBSE Last year with 91% . An really I did not know about normalisation process much , But I think with 90% + in CBSE board and atleast 230-240 marks are requaired in Mains to get okay NIT, But as competition is increses day by day so we can't predict. So it is better to perform Better in JEE Mains and leave rest on our Luck . @manish bhargao

- 5 years, 4 months ago

Can you please solve them and post solution....thnkx problem 1 Problem 2

- 5 years, 4 months ago

- 5 years, 4 months ago

Does anyone know why the old uncle's amazed ?

Let me tell you .

He saw into the future and was surprised to see that @Deepanshu Gupta had created a note named DEEPANSHU GUPTA's MESSAGE BOARD 10 .

Believe me friends , the old uncle never lies , and for further proof , just check tha number of replies this note has acquired in a really short span of time !!

- 5 years, 4 months ago

Ha ha ha !! Lol ! :) I wish that this won't happen . It is really difficult for me for replying .

- 5 years, 4 months ago

Currently I am getting an average of 7 notifications every minute . I can imagine your condition !!

- 5 years, 4 months ago

$\huge XD$

- 5 years, 4 months ago

yes It's undefinable. :)

- 5 years, 4 months ago

Hey Deepanshu, I wanna tell you that your Mechanics questions are really awesome and quite different from conventional ones.

Keep posting them.

And, Best of Luck for JEE.

- 5 years, 4 months ago

Thanks Ninad ! Yes I will make some more question's right after my JEE main's exam . Since Now day's i'am focussing on my speed and accuracy ! But after Main's I will surly Post . @Ninad Akolekar $\ddot\smile$

- 5 years, 4 months ago

Exactly and I think you might be referring to the $Balti$ question , right ?

- 5 years, 4 months ago

Pls suggest books fr jee, especially organic n physics( except irodov)

- 5 years, 4 months ago

Hello friend! Can you tell me how did you solve this question. The title says to solve geometrically, but I can't even solve it algebrically What method did you adopt? Please Help!

- 5 years, 4 months ago

Hi friend ! , Actually I don't know geometric method right now , But Yes I solved it by algebric method. Hint : Make that equation as perfect square ! @Samuel Jones

- 5 years, 4 months ago

How did you started physics?

- 5 years, 4 months ago

will you please elaborate what did you mean exactly ? I didn't get you . Thanks!

- 5 years, 4 months ago

Wanted to know which topic interested you the most , how much time you devoted to physics , whether your mind made a decision to do only physics leaving other subjects? Lastly my same question from where I need to start and get a keen interest in it?

- 5 years, 4 months ago

@U Z Well In Physic's I like everything related to physics , But Yes I most like " Heat and Thermodynamics " and also Space Science is quite fascinating. I did not have specific time table but yes i can tell u what i did this year , after coming from my coaching I didn't revise my notes , I just do challanges of each subject (one of each subject's) which was given to us by our teacher's in homework. I take time , But Solved it untill it can't solved , I don't give up. I see that doing so I'am able to solve all question's or getting almost close to solution of that challanges after some time. So I Just build up my Confidence , and always talk to myself that I can solve any problem of physic's , since I know concept's like other's know's. So this attitude really Help's me . And Also I did not do any much homework , like doing dpp's , sheet's , etc. Except for chemistry , For chem. I studied my theory notes regularly and solve my worksheet's properly! But For physic's and math's I just Think question's concept , rather than doing more and more problem . This Level up my thinking. I have suffecient time since I don't have to go school's . I really Study Physics very carefully , I hear every single thing from my teacher's . Always try to relate situation's with realty. I feel every problem and co-relate it with real life.
If You want to develop nterest in physic's as well , then I suggest you , after reading any physic's question try to relate it with your life , and say's wow ! what a real situation , believe me by doing so you will find that new interest will developing in you ! Also I suggest You To read small history of chapter's ,Like who/how/why/ invent this believe me it gives u new positive energy and new interest will develop in you . Important thing is that you must have to believe in yourself that " I can Solve Every problem of physic's " . So believe in yourself and be confident. Also Say's to yourself that you love physic's . So feel physics , enjoy physics ! You will suerly get expertise in it .Best of luck ! $\ddot\smile$ Feel free to ask me further any thing ! I'am glad to help my brother @megh choksi

- 5 years, 4 months ago

It feels great to read you advises related to Physics !! But I always have a problem co-relating the question with reality , most of the time I get it wrong !!

But I still keep trying , hoping that someday I might get the knack of it .

- 5 years, 4 months ago

Nope , Instant Notes in Phy Chem isn't that good , it just contains info abt Virial Equation , which is too simple a topic .

Going back to the original point ,resonance DLPD material is the best for Phy Chem .

- 5 years, 4 months ago

Thanks ! I know one of my friend , who is in resonance , I will suerly take his study material ,!

- 5 years, 4 months ago

I didn't realize it till now that I hadn't followed you !!!!

I was always wondering why did I never get your questions in my Community Feed directly , always it would be reshared by someone else .

Darn! I also missed the opportunity of being your 500th follower :(

- 5 years, 4 months ago

i was his 500 follower.

- 5 years, 4 months ago

Congrats :)

- 5 years, 4 months ago

$\huge \text{Thanks for your advice}$ I have just returned after writing the exam !!

Btw the paper was toooooo lengthy . The exam was scheduled from 10 : 30 am to 1:30 pm , you know what , I completed my paper at 1:27 pm .

And yeah , my handwriting went from Italics to a font style that is not yet defined !! Also the paper was quite easy :)

- 5 years, 4 months ago

that's good , english paper is alway's being lengthy . I feel good that you did well . Gud luck for next exam ! $\ddot\smile$

- 5 years, 4 months ago

Can you provide solution to this problem

- 5 years, 4 months ago

All The Best Bro! :D

- 5 years, 4 months ago

Do you like carrots?

- 5 years, 4 months ago

Instead of directly eating carrot's , I Prefer to eat " Gajar Ka Halwa " . I really Love to eat that " halwa " . Interesting thing is that my father prepare very delicious " Halwa " instead of my mom . Even currently and whenever I'am doing Brilliant .org I ate "Gajar ka halwa" . It is sad that my father said that this is probably Last time in this season . Since carrot's season going to off air . @Agnishom Chattopadhyay $\ddot\smile$

- 5 years, 4 months ago

Just curious, would you ask this to me also if I post a message board

- 5 years, 4 months ago

sure

- 5 years, 4 months ago

Sorry I forgot , Congrats for getting 400 followers !!!

But I believe that I'll be congratulating you again in a few days , am I right ?

- 5 years, 4 months ago

Thanks! I'll be congratulating you back at that time.

- 5 years, 4 months ago

Haha , honestly I was expecting this question to come up !! Though I was expecting someone else to ask it :)

- 5 years, 4 months ago

Hi Deepanshu! Congratulation on achieving the milestone of 500 followers. I want to ask you, when should one start preparing for JEE? When you started preparing for it? I recently downloaded book named 'Classical Mechanics' by David Morin. And I found new fascinating things like Catenary equations, Polar coordinates, Rotating frame of reference etc. I want to ask you are these things required for JEE.

I liked your new profile pic. :)

- 5 years, 4 months ago

Hi Satvik , My sweet Brother ! Thank's .
And I think there is no particular age for starting JEE prep. Even when I'am in 10th I didn't hear about JEE once , I come to know after entering in 11th , and due to which i struggled intially , but then everything's okay, and Particularly I didn't solve much book's , instead I prefer to study in depth and in meaningful way , I enjoyed physic's , and I don't think that if a person want's to do well Particularly in JEE (I'am not talking of olyimpiad's yet) , then he had to finished all book's , including Krotov , David moroin , These book's have really good bunch of problem's but they actually used blending's of concept's , so it doesn't guaranteed that we understand better physic's , and studying various topic's which are not in syllabus , is not necessary , because, think if it is good for us , then why they did not include it in our current topic's ? actually It is beacuse everything has particular time for understand it in better way , we will surly studied it in depth in engg. Since JEE paper is not based on blending's , they only enforce in making question which need's some thinking , which is required for making good engg. , Since In all such book's there are question's which need's blending's , they did not use so much thinking (I'am not taliking of , thinking like that how can I integrate this question's solution etc this is not realistic physic's) So it is not good to read such topic's in half knowledge , because half knowledge is dangerous than zero knowledge . I Have my old friend's which get AIR: 58 ,187 ,858 etc. in JEE , doesn't know about such book's , and they even do not try IRADOV once , also they don't know about beta/gamma/zeta function's in Integral calculus , they only enforce to study in depth and in meaningfull way, They alway's said that they wiill study it in IIT's in meaningfull way , since everything's have appropriate time .

But , if one preaparing for olyimpiad's etc. then Solving such Book's is really important , and very helpfull . and also You were in 11th , and i think that you already completed mechanic's , so I think you have suffecient time for reading and solving such stuff's .
Note : This are only my view's . Don't take it so seriously :) All The Best for your Board's :) @satvik pandey

- 5 years, 4 months ago

Thank you @Deepanshu Gupta and @Mvs Saketh for guiding. I too feel that solving hard problems like those which are present in that book is not necessary for cracking jee. But at the same time I am very much interested in Mechanics. I like to explore different, new and fascinating concepts of mechanics. So, I would try to study that book but at the same time I will make sure that reading that book doesn't compromise with my JEE preparation. Thank you guys for guiding me. You guys are very nice to me and I have learned a lot from you guys. :)

This note has too many replies. It took 10 minutes to find replies of you guys!:D

- 5 years, 4 months ago

Lol ! Even I had to struggled for Replying all my friend's .

- 5 years, 4 months ago

Calvin lin msgboard 2 has "only" 295 replies.around 90 to go.

- 5 years, 4 months ago

Yeah, considering the fact that C L M Board was created in Jan , no ?

- 5 years, 4 months ago

boss is always right.

- 5 years, 4 months ago

Just 1 day and 23 hours and it has 209 replies !! Just imagine after 1 week !!

- 5 years, 4 months ago

I am remembering finn hulse's note exponential growth 1000 reshares and laughing.

- 5 years, 4 months ago

- 5 years, 4 months ago

I found it somewhere in Brilliant

- 5 years, 4 months ago

Thanks bro :)

- 5 years, 4 months ago

That is the most awesome book in mechanics ever written, i strongly suggest you fully study it(atleast as far as possible), @satvik pandey

believe me david morin has so nicely explained everything that your concept will be totally clear by the time you finish the chapters, you have lots of time still in 11 th class so make full use of it, unfortunately i only came to know of it in 12th class still i finished it (except some chaps of special relativity, general relativity, parts of largrangian mechanics and a bit of statics and few probs here and there) when i was preparing for INPHO in January, i just cant put how awesome it is, but i hope you realise it, because anyone who reads it will love mechanics for sure.

- 5 years, 4 months ago

Thank you Saketh and Karthik.

I will surely go through it after my class 10 boards. I started studying it but when it came to tension in massive string and catenary equations it seemed to be very much complicated( mainly the mathematical part). Also the problems given in that book seemed to be very much complicated and difficult. I was going through the chapters of rotational mechanics and I saw that it contain lots of new and fascinating concepts. like rotating frame of reference etc. I want to ask you are these things required for cracking JEE? As I like Mechanics very much so I strongly want to study that book. But I want to make sure that this doesn't compromise my JEE preparation starting from the next month.

- 5 years, 4 months ago

Dont start from Statics, you will be bored, I suggest you start from conservation of linear momentum and energy, and study first, dont directly go to problems even if you can likely solve most of them, also it is useful chapter from IIT JEEs point of view as well, after that do the chapter 7 , (the first angular momentum chapter, skip the derivations or derive simpler versions if the math hurts your head (till the time when you will be able to properly understand them)) and do it thoroughly, these two come in JEE and your concept will become extremely clear (it already is , but trust me it will help) after that solve their questions completely, you will naturally want to learn more and you will yourself grasp with other chapters , and no it will not compromise with your JEE prep, infact you better do now because after NSEP, if you wish to qualify INPHO, that is definitely recommended, infact it is a recommended olympiad book in many countries, But make sure that you are not only doing that but also the electromagnetism of DC pandey etc and ofcourse Math and Chem. i assure you no harm shall be done, its your choice however.

and trust me it is hard, not just for you anyone , i too found it hard at first, but carefully think and you will realise that most problems are simple :)

finally know that i was at a much worse position than you in 12, i could barely understand newtons laws, frankly Only in 12th class, i studied both 11th and 12th course (i do not recommend that) yet i had time for it, Whereas you are in a much better position, so go for it, but remember, the more you learn math, the better you can do physics , and the better you can qualitatively predict chemistry Best of luck!

- 5 years, 4 months ago

Yeah it indeed is a great book. Unfortunately I too got to know about it only after the JEE.

- 5 years, 4 months ago

So finally you have created a message board , and congrats on 500 followers .

Your Physics questions are awesome , they are too tough for me to solve , hope you'll keep on posting such awesome questions .

I think that you know that we have our first exam , English , tomorrow , do you have any tips regarding how to maintain composure and any such stuff regarding Board exam (not English in particular) ?

PS I didn't give Board exam in class 10 , so I'm a bit nervous, you see !!!

- 5 years, 4 months ago

thank you :) , I will try to make question after our main's exam . And Best of Luck For Your Board's . I suggest You to keep calm and cool , Believe me, CBSE Paper checking is very- very easy ( believe me ), You will definitely Got Lot more than you ever then expected , For English Just make your impression on teacher's by using a few tough word's . Don't try to elongate your answer too much , instead use some typical and beutiful word's , and Keep Time in your Mind , I'am saying beacuse I had left my 10 mark's , So i don't want that it happened to you . And for other's subject's I prefer you to solve Old year Paper's (It is must for physics and chemistry ) , they really help lot , and makes you handy ! Chemistry Paper is genrally finished in 2 hour's atmost, Since I fineshed it last year .Write two the point's in chemistry specially . For Physic's important derivation's are need to done atleast twice . Practice for diagram . You can impart your knowledge in paper in intiall 2-3 question , so that teacher's definately take interest in your paper ! But BE CAREFULL , don't waste too much time , otherwise it will give you Pain . Listen some soft music's in breaks of studies . Best of Luck my brother , Rock It $\ddot\smile$

- 5 years, 4 months ago

I'll try to finish the paper in time , thanks for sharing your experience with me :)

- 5 years, 4 months ago

$\huge\text{You post good problems! ! }$

- 5 years, 4 months ago

Which is your strongest part out of Maths, Physics, and Chemistry ?

And what are you expectations in JEE-Mains and JEE-Advanced as per your preparation ?

- 5 years, 4 months ago

I can't say about topic's in which I'am stronger or not , I love everything related to math's , physic's .

But yes for Math's , Complex Number's is One of my favourites topic's . Due to it's wide application's it fascinates me very much . And Calculus is also one of those topic's . Although I did not now much about Integral calculus , Like I see other student's know's . I only Know's Basic Integration , I did not studied gamma , beta function's yet etc. But I'am curious to learn and will surely study in Engineering.

For Physic's , I love each and every thing even i like every single thing abot physic's , I'am really mad about physic's and always wanted to learn more and more . It lives in my heart forever , I'am just wanted to swimming in the pool of Physic's . I can't say that I'am strong in particular topic , But yes again , thermodynamics is my fav. sectiion , I want to do research in Energy or Robotic's , after completing my graduation in Mechanical Engg. (If I will get :) )

For chemistry , I hope this is my last year for chemistry :P , I read Enough chemistry in my life ,. But Yes I can study Organic chemistry in my engg. if I have to .. !

And Expectation's are always high and can't be fulfilled completely ever , But as of now , since JEE main's is nearer so i think I can score 80-85 % in JEE main's . If everything goes well . And For Advance I can't comment yet , I can comment on it probably in may , Since I have time to prepare better for it. !$\ddot\smile$ @Sandeep Bhardwaj Sir

- 5 years, 4 months ago

i m sure you would calculate depth of swimming pool use wave mechanics instead of a "metre" scale of "infinite metres",isn't it?

- 5 years, 4 months ago

Lol , a metre scale wouldn't be called as a "Metre " scale if it was of infinite length :D

- 5 years, 4 months ago

Pun intended.(english paper recall definition of pun)

- 5 years, 4 months ago

Thank you! Great, keep it up and all the best ! @Deepanshu Gupta

- 5 years, 4 months ago

From where did you learn doppler's effect? Your concepts about doppler's effect and newtonian mechanics are damn very strong....so can you please guide regarding these topics..?

- 5 years, 4 months ago

Actually was taking coaching's for it , from Bansal Classes, jaipur! Newtonian mechanic's really very interesting and easy topic . First thing I recommend you that , " Be confident" and " Believe in yourself " , really I was not so good in mechanic's last year , due to careless study in 11th class , So I have Low confidence . This I realise that intelligence is nothing . It's only depend's on how you enjoy your study's and how's is your confidence. If you wan't to expertise in mechanic's then first say one thing to yourself , "I Love mechanic's and I can do any problem in mechanic's " , beacuse matter is not that , you know less , but matter is that how confident you are to apply all knowledge , which you gain till know . So belief in yourself , and try to co-relate problem's with your real life , this give's you a kind of " feel" which i can't express in word's . And after your Board try to solve problem's with relating it with your real life , and see the magic ! So have gud luck for your upcoming future ! $\ddot\smile$ @Mahimn Bhatt

- 5 years, 4 months ago

I agree completely.

- 5 years, 4 months ago

- 5 years, 4 months ago

@Deepanshu Gupta Can you please minimise acos(x-y) + bcos(y-z) + c cos(z-x)

where a,b,c are known constants, just minimise, no need to find the values of x,y,z for that,

or atleast give a hint :) thanks

- 5 years, 4 months ago

Is the answer $\dfrac{a^2b^2 + b^2c^2 + c^2a^2}{2abc}$ ?

- 5 years, 4 months ago

I have solved it bro, now i dont know the explicit expression as i directly input values and solved,

but your answer is correct, , the answer is 29 I got it the partial derivative way,

a=12 b=24 c=16

- 5 years, 4 months ago

@Mvs Saketh Try it differently. The solution to that question was of course, posted by the author of this message board(coincidence?). Try to do it (complex)algebraically. I followed this approach and got stuck somewhere around here.

- 5 years, 4 months ago

Done :) but used my way only ,

- 5 years, 4 months ago

Are you trying the problem Too Complex to solve

- 5 years, 4 months ago

indeed

- 5 years, 4 months ago

Heres my progress, since it is invariant under rotation (that is only the relative position of x,y,z matter)

so i can fix any one of them, so i fixed x=0

to get a resultant equation, here however i cannot do what i want ,

the resultant equation is simply

$acos(y)\quad +\quad bcos(z)\quad +\quad c\quad cos(y-z)=f$

so i tried to use partial differentiation to equate

$\frac { \delta f }{ \delta y } =0\quad =\quad -asin(y)\quad -c\quad sin(y-z)\\ \\ \frac { \delta f }{ \delta z } =0\quad =\quad -bsin(z)\quad +\quad c\quad sin(y-z)$

This is solveable now ( i have posted the solution in the respective problem),, i was hoping for some geometric insight,

- 5 years, 4 months ago

I think there is. Just try and correlate the above expressions with law of sines and the use the law of cosines in the given expression.

- 5 years, 4 months ago

Thanks i shall try that way :)

- 5 years, 4 months ago

If x,y,z are not distinct , then obeviously answer will be a+b+c . Could You Please Specify whole question please @Mvs Saketh

- 5 years, 4 months ago

i am sorry, not maximise, minimise, i am really sorry, you see bro, to minimise, i thought it might be -a-b-c, but for that we need x-y = (odd) pi and y-z = (odd)pi and x-z= odd(pi)

but the problem is (x-z) = (x-y+y-z) = (x-y) +(y-z) = odd pi + odd pi = even pi,

which contradicts, hence all cant be minimum or -1 simultaneously,

- 5 years, 4 months ago

Give me a chance , I will Try it .... wait what are x,y,z ?

- 5 years, 4 months ago

varriables, belong to R, but for convenience you may restrict domain to (0,2pi) it wont affect

- 5 years, 4 months ago

If you don't mind, can you please tell me from where do you study physics??

- 5 years, 4 months ago

Actually I go to coaching , and if you are asking for book's , then I did not use book's as much , rather i prefer to study in depth and in meaningfull way. So thing's will automatically going simple , But Yes I some time Prefer H.C Verma for practising ! @Harsh Shrivastava

- 5 years, 4 months ago

Thanks!

Best oF LUCK for JEE!!

ALSO "wewontgiveitback"

- 5 years, 4 months ago

Thanks ! Ha ha ha , Yes sure , we " Won'tGiveItBack " :)

- 5 years, 4 months ago

How are you preparing for jee and how are studies going? Congrats 500 followers and a mesasgeboard.

Your status is really awesome Mauka -Mauka , I also adopted that .Nice profile pic.

- 5 years, 4 months ago

Thank you , I love this add series very much , Hope we will continued our streak in world cup !

- 5 years, 4 months ago

Thanks, It's fine , Currently I'am Focusing on Revision of chemistry , I'am reading theoretical chapter's , and solving previous Year JEE main's and advance Paper's , also model's paper's . Also focussing on my Speed , Like I hide my calculator ! So overall it's fine ! $\ddot\smile$ @GAUTAM SHARMA

- 5 years, 4 months ago

cool!!

- 5 years, 4 months ago