If $y=y(x)$ and $\frac{2sin \, x}{y+1}\frac{dy}{dx} = -cos \, x, y(0) = 1, $ then $y (\pi /2)$ equal |
$\frac{1}{3}$ $\frac{2}{3}$ $-\frac{1}{3}$ 1 |
$\frac{1}{3}$ |
The correct answer is option (1) : $\frac{1}{3}$ $\frac{2sin \, x\, }{y+1}\frac{dy}{dx} = -cos \, x$ $⇒\frac{1}{y+1}dy =-\frac{cos\, x}{2+sin x}dx$ $⇒∫\frac{1}{y+1} dy = - ∫\frac{cosx}{2+sinx}dx$ $⇒kog (y+1) = - log (2+sin x) + log C$ $⇒y + 1 = \frac{C}{2+sin x}$ Putting $x = 0$ and y = 1 in (i), we get $2=\frac{C}{2} ⇒ C=4$ Putting $C=4$ in (i), we get $y +1=\frac{4}{2+sin x}$ Putting $ x=\frac{\pi }{2}$, we get $y + 1=\frac{4}{3} ⇒ y =\frac{1}{3} ⇒ y \left(\frac{\pi }{2} \right ) = \frac{1}{3}$ |