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# Tricks and concepts

The objective of this note is to know and tell about the concepts, techniques or tricks which may be helpful during our Jee-prepration and are rather not that popular ( i.e you do not learn them commonly in school or maybe not at coaching too .) so, it will just take few seconds to write down (Our target would be to give at least a concept daily ) but it will help us all ! you may also write something important ( only related to study ) so that you may see it later , It would be great if you all make this note an important one such that we will see it a day or two before jee advanced !  Rules : if you are contributing something , write it's number after 2 hashtags and comment and if you are just commenting , write normally !  ##Enjoy !

Note by Shubham Dhull
5 months, 2 weeks ago

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## 5  Whobbling coin : concept is very important, you can learn it here : coin or here .....there are some nice question on brillant related to it too .............. 1 or 2 { although , i solved both of them without learning the concept :P }

· 5 months, 2 weeks ago

It is not in the syllabus I guess? · 5 months, 2 weeks ago

yes , but in jee-advanced question can be asked as we saw in jee adv. -2016 that they are shifting their focus from normal to some good level physics ! :) · 5 months, 2 weeks ago

## Using Feynman's method of integration can be useful in scenarios where there is a natural logarithm on the numerator of the integrand.

· 5 months, 2 weeks ago

## method of this trick is to differentiate the integral w.r.t to a constant and then integrate normally !!

· 4 months, 4 weeks ago

Yeah.

For example,consider this :

$$\displaystyle \int_{0}^{1}\dfrac{1-x^{2016}}{\ln x} dx$$

It can be easily solved by using feynman's method! · 4 months, 4 weeks ago

care to show , how ? · 4 months, 4 weeks ago

$$F(a) = \displaystyle \int_{0}^{1} \dfrac{1-x^{a}}{\ln x}dx$$

$$\implies F'(a) = \displaystyle \int_{0}^{1} \dfrac{-x^{a} \ln x}{\ln x}dx = \displaystyle \int_{0}^{1} -x^{a}dx$$

Now rest is easy i guess. · 4 months, 4 weeks ago

but bro @Harsh Shrivastava both of them yield different result ! :O , first will give -log(2017) while second one 1/2017 , there is difference of that log ! · 4 months, 4 weeks ago

your concept is wrong bro ! · 4 months, 4 weeks ago

Comment deleted 4 months ago

Well no need to be sorry bcoz I am not in class 12, I m in class 11.

I'll give some awesome application of these tricks in a few days. · 5 months, 2 weeks ago

Comment deleted 4 months ago

Yeah :(

Gone are the days when people used to be online, now where are the gone.

Please contribute guyz @Aniket Sanghi @Prakhar Bindal

BTW how is your preparation going? · 5 months, 2 weeks ago

Like i came online for typing answer to this problem

https://brilliant.org/problems/frac1falling-space-rod/

i had taken a note of it some time before · 5 months, 2 weeks ago

Actually i hardly see my notifications these days. just when i am bored i open brilliant see a problem take a note of it and then go back again to my room for solving · 5 months, 2 weeks ago

Comment deleted 4 months ago

Lol I meant they are not active anymore.

Best of luck! · 5 months, 2 weeks ago

https://brilliant.org/problems/a-simple-integral-3/

This problem's solution contains some awesome results that are hell useful. · 5 months, 2 weeks ago

solved it, was nice ! · 5 months, 2 weeks ago

## 3  Descartes rule of signs : Again , not that uncommon but useful "trick for finding the roots of a quadratic ! You can learn it here or here

· 5 months, 2 weeks ago

## 9 Some expansions and special series and suggest you remember them too ! :) taylor and basel problem types

· 4 months, 4 weeks ago

## 7  i am tired of writing "not that uncommon" but here are cauchy-swartz and generalized mean theorm

· 5 months, 1 week ago

Cauchy schwarz is really really awesome and useful for manyy problems! · 4 months, 4 weeks ago

## 6  common sense :P

· 5 months, 2 weeks ago

I have posted our challenge problem,do try it! · 5 months, 2 weeks ago

## 2  Abel's theorm for power series : you can learn it here Abel it is useful for calculation of some power series expansion ! you can see other theorms given by Niels Henrik Abel in the related links on wikipedia !

· 5 months, 2 weeks ago

## 1  I will begin by giving information about a method called method of images(not that rare but helpful sometimes !)  for hindi speaker this will be the best explanation or maybe this : wiki  there is a nice question on brilliant too on it here , it deals with the quantitative analysis of charge induced on an equipotential surface !

· 5 months, 2 weeks ago

Images are useful in many problems in I E Irodov's book · 5 months, 2 weeks ago

yeah ! that's why i told it and also wrote (not so rare , if you have some concept to share , do write it ! ) · 5 months, 2 weeks ago

I have a method which will solve Irodov's Mechanics Q1.82 in 3 steps. How did you do it? · 5 months, 2 weeks ago

drew fbd's and constraint of string length i did in 3-4 steps too ! which method do you wanna propose bro @Kishore S Shenoy ? · 5 months, 2 weeks ago

Balanced horizontal forces and acceleration along the wedge to get acceleration. · 5 months, 2 weeks ago

## 8 From me too bro : link

· 5 months ago

thanks for mentioning me , bro this sounds cool .. i have some stuff related to the electrical ckts , capacitors and lemme find out more .. · 5 months, 2 weeks ago