## Excel in math and science

### Master concepts by solving fun, challenging problems.

## It's hard to learn from lectures and videos

### Learn more effectively through short, conceptual quizzes.

## Our wiki is made for math and science

###
Master advanced concepts through explanations,

examples, and problems from the community.

## Used and loved by 4 million people

###
Learn from a vibrant community of students and enthusiasts,

including olympiad champions, researchers, and professionals.

## Comments

Sort by:

TopNewestConstruct point I, which is the reflection of D about FE.

\(\alpha = \angle IHE\)

\(\alpha+\beta = \angle IHE + \angle EHC = \angle CHI\)

Connect CI. Note that \(\triangle HCI\) is a right angled isosceles triangle, thus \(\angle CHI = 45^\circ \)

\(\gamma = 45^\circ\)

Thus sum of 3 angles \(=90^\circ\)

Log in to reply

Thank you!

Log in to reply

answer =90

Log in to reply

y=45degree. alpha+ beta= 45 degree as tan ( a + b)= tan a + tan b /(1-tan a * tanb)= (1/2+1/3)/(1-1/2*1/3)=1 =90 degree.

Log in to reply

90 degree!! tan^-1(1)+tan^-1(0.5)+tan^-1(1/3)=90

Log in to reply

This was in our fiitjee booklet last year.Quite easy

Log in to reply

Log in to reply