MCQ
The value of $\frac{e^{-\frac{\pi}{4}}+\int \limits_0^{\frac{\pi}{4}} e^{-x} \tan ^{50} x d x}{\int \limits_0^{\frac{\pi}{4}} e^{-x}\left(\tan ^{49} x+\tan ^{51} x\right) d x}$ is
  • $50$
  • B
    $49$
  • C
    $51$
  • D
    $25$

Answer

Correct option: A.
$50$
a
$\int \limits_0^{\pi / 4} e^{-x} \tan ^{50} x d x$

$\left[-e^{-y}(\tan x)^{50}\right]_0^{\pi / 4}+\int \limits_0^{\pi / 4} e^{-x}(50)(\tan x)^{49} \sec ^2 x$

$=-e^{-\pi / 4}+0+50 \int \limits_0^{\pi / 4} e^{-x}(\tan x)^{49}\left(\tan ^2 x+1\right)$

$=-e^{-\pi / 4}+50\left(\int \limits_0^{\pi / 4} e^{-x}(\tan x)^{51}+(\tan x)^{49}\right) d x$

Now,$\frac{-e^{-\pi / 4}+\int \limits_0^{\pi / 4} e^{-x}(\tan x)^{50} d x}{\int \limits_0^{\pi / 4} e^{-x}\left(\tan ^{49} x+\tan ^{51} x\right) d x}$

$\frac{50 \int \limits_0^{\pi / 4} e^{-x}\left((\tan x)^{51}+(\tan x)^{49}\right) d x}{\int \limits_0^{\pi / 4} e^{-x}\left(\tan ^{49} x+\tan ^{51} x\right) d x}=50$

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