Medium INTEGER +4 / -1 PYQ · JEE Mains 2021

If $y = y(x),y \in \left[ {0,{\pi \over 2}} \right)$ is the solution of the differential equation $\sec y{{dy} \over {dx}} - \sin (x + y) - \sin (x - y) = 0$, with y(0) = 0, then $5y'\left( {{\pi \over 2}} \right)$ is equal to ______________.

Answer (integer) 2

Solution

$\sec y{{dy} \over {dx}} = 2\sin x\cos y$<br><br>${\sec ^2}ydy = 2\sin xdx$<br><br>$\tan y = - 2\cos x + c$<br><br>$c = 2$<br><br>$\tan y = - 2\cos x + 2 \Rightarrow$ at $x = {\pi \over 2}$<br><br>$\tan y = 2$<br><br>${\sec ^2}y{{dy} \over {dx}} = 2\sin x$<br><br>$\therefore$ $5{{dy} \over {dx}} = 2$

About this question

Subject: Mathematics · Chapter: Differential Equations · Topic: Order and Degree

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