JEE Main Solved Paper 2017 Question 16

Question: If $ (2+\sin x)\frac{dy}{dx}+(y+1)\cos x=0 $ and $ y(0)=1, $ then $ y( \frac{\pi }{2} ) $ is equal to:- [JEE Main Solved Paper-2017]

Options:

A) $ \frac{4}{3} $

B) $ \frac{1}{3} $

C) $ -\frac{2}{3} $

D) $ -\frac{1}{3} $

Show Answer

Answer:

Correct Answer: B

Solution:

$ (2+\sin x)\frac{dy}{dx}+(y+1)\cos x=0 $

$ \frac{d}{dx}(2+\sin x)(y+1)=0 $

$ x=0,y=1\Rightarrow c=4 $

$ y+1=\frac{4}{2+\sin x} $

$ y( \frac{\pi }{2} )=\frac{4}{3}-1=\frac{1}{3} $