Differential Equations Question 340

Question: If $ \frac{dy}{dx}+\frac{1}{\sqrt{1-x^{2}}}=0 $ , then

[MNR 1983]

Options:

A) $ y+{{\sin }^{-1}}x=c $

B) $ y^{2}+2{{\sin }^{-1}}x+c=0 $

C) $ x+{{\sin }^{-1}}y=0 $

D) $ x^{2}+2{{\sin }^{-1}}y=1 $

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Answer:

Correct Answer: A

Solution:

$ \frac{dy}{dx}=-\frac{1}{\sqrt{1-x^{2}}} $

Therefore $ dy=-\frac{1}{\sqrt{1-x^{2}}}dx $

On integrating, we get $ y={{\cos }^{-1}}x+c $

Therefore $ y=\frac{\pi }{2}-{{\sin }^{-1}}x+c $

Therefore $ y+{{\sin }^{-1}}x=c $ .