MCQ
If $\frac{d y}{d x}=y \sin 2 x, y(0)=1$, then solution is
  • $y=e^{\sin ^2 x}$
  • B
    $y=\sin ^2 x$
  • C
    $y=\cos ^2 x$
  • D
    $y=e^{\cos ^2 x}$

Answer

Correct option: A.
$y=e^{\sin ^2 x}$
(a) : We have, $\frac{d y}{d x}=y \sin 2 x$
$
\Rightarrow \quad \frac{d y}{y}=\sin 2 x d x \Rightarrow \log y=-\frac{\cos 2 x}{2}+C
$
Since $y(0)=1 \Rightarrow x=0, y=1 \Rightarrow C=1 / 2$
$
\therefore \quad \log y=\frac{1}{2}(1-\cos 2 x) \Rightarrow \log y=\sin ^2 x \Rightarrow y=e^{\sin ^2 x}
$

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