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Calculus Level 5

1 1 + sin 2 x dx = ? \large \displaystyle\int \dfrac{1}{1 + \sin 2x} \text{dx} = \ ?

Note : C is integration constant.

tan ( π 2 x ) \tan\left( \dfrac{\pi}{2} - x\right) + C None of these tan ( π 4 x ) \tan\left( \dfrac{\pi}{4} - x\right) + C 1 2 tan ( x π 4 ) \dfrac{1}{2} \tan\left( x - \dfrac{\pi}{4}\right) + C 1 1 + tan x \dfrac{1}{1 + \tan x} + C 1 1 + cot x \dfrac{-1}{1 + \cot x} + C 1 2 tan ( x π 2 ) \dfrac{1}{2} \tan\left( x - \dfrac{\pi}{2}\right) + C

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2 solutions

Akhil Bansal
Oct 17, 2015

I = 1 1 + sin 2 x dx \Rightarrow \text{I} = \int \dfrac{1}{1 + \sin 2x} \text{dx} I = 1 1 + cos ( π 2 2 x ) dx \Rightarrow \text{I} = \int \dfrac{1}{1 + \cos\left( \dfrac{\pi}{2} - 2x\right)} \text{dx} I = 1 2 cos 2 ( π 4 x ) dx \Rightarrow \text{I} = \int \dfrac{1}{2\cos^2\left(\dfrac{\pi}{4} - x\right)}\text{dx} I = 1 2 sec 2 ( π 4 x ) dx \Rightarrow \text{I} = \dfrac{1}{2} \int \sec^2\left( \dfrac{\pi}{4} - x\right) \text{dx} I = 1 2 tan ( x π 4 ) + C \Rightarrow \text{I} = \dfrac{1}{2}\tan\left( x - \dfrac{\pi}{4}\right) + \ C
O R \Large \color{#3D99F6}{OR}
I = 1 1 + sin 2 x dx \Rightarrow \text{I} = \int \dfrac{1}{1 + \sin 2x}\text{dx} I = 1 1 + 2 tan x 1 + tan 2 x dx \Rightarrow \text{I} = \int \dfrac{1}{1 + \dfrac{2\tan x}{1 + \tan^2x}}\text{dx} I = 1 + tan 2 x ( 1 + tan x ) 2 dx \Rightarrow \text{I} = \int \dfrac{1 + \tan^2 x}{(1 + \tan x)^2}\text{dx} substituting tan x = t sec 2 x dx = dt \text{substituting}\ \tan x = t \Rightarrow \sec^2x \text{dx} = \text{dt} I = 1 1 + tan x + D \Rightarrow \text{I} = \dfrac{-1}{1 + \tan x} + \ D We can add 1 2 to our integration as it’s a contant \text{We can add}\ \dfrac{1}{2} \ \text{to our integration as it's a contant} I = 1 1 + tan x + 1 2 + C \Rightarrow \text{I} = \dfrac{-1}{1 + \tan x} + \dfrac{1}{2} + \ C I = 1 2 tan ( x π 4 ) + C \Rightarrow \text{I} = \dfrac{1}{2}\tan\left( x - \dfrac{\pi}{4}\right) + \ C

Dude, I am getting sin x cos x + sin x \dfrac{\sin{x}}{\cos{x}+\sin{x}} , how will you simplify it.

Department 8 - 5 years, 7 months ago

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Can you please elabotate how did you got that ?

Akhil Bansal - 5 years, 7 months ago

I did by second method and I didn't thought to add or subtract a constant. Good one!!😀😀

Anurag Pandey - 4 years, 10 months ago

Download directly to brain 😂😂😂😂

Sahil Silare - 4 years, 2 months ago

Adding that constant was the trick of the question , otherwise the question was flat

Prithwish Mukherjee - 2 years ago
Pulkit Gupta
Dec 8, 2015

Writing 1 + sin 2 x \sin 2x as { sin x \sin x + cos x \cos x }^2 and then simplifying it to a single cosine term simplifies the integral greatly.

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