Q25 / 116 · NTA Abhyas (JEE Main) 2020 · Mathematics · Definite Integration

The value of the integral Ι=∫0∞dx1+x20201+x2 is equal to kπ, then the value of 16k is equal to

Correct answer: 4

Solution

Put tan-1x=θ
⇒x=tan⁡θ
⇒dx=sec2θdθ
⇒Ι=∫0π/2sec2θ1+tan2020θsec2θdθ
=∫0π2dθ1+tan2020θ
Ι=∫0π2cos2020θcos2020θ+sin2020θdθ
Applying a+b-x property and adding, we get,
2Ι=∫0π2cos2020θ+sin2020θcos2020θ+sin2020θdθ
⇒2Ι=θ0π2=π2-0
⇒Ι=π4
⇒k=14⇒16k=4

Hence, the correct answer is 4.

More Definite Integration Questions