MCQ
Solution of the differential equation $\frac{{dy}}{{dx}}\tan y = \sin (x + y) + \sin (x - y)$ is
  • $\sec y + 2\cos x = c$
  • B
    $\sec y - 2\cos x = c$
  • C
    $\cos y - 2\sin x = c$
  • D
    $\tan y - 2\sec y = c$

Answer

Correct option: A.
$\sec y + 2\cos x = c$
a
(a) $\frac{{dy}}{{dx}}\tan y = \sin (x + y) + \sin (x - y)$

$\frac{{dy}}{{dx}}(\tan y) = 2\sin x\cos y$ ==> $\frac{{\sin y}}{{{{\cos }^2}y}}dy = 2\sin xdx$

==> $\int {\frac{{\sin y}}{{{{\cos }^2}y}}} dy = 2\int {\sin xdx} $ ==> $\frac{1}{{\cos y}} = - 2\cos x + c$

$\therefore$  $\sec y + 2\cos x = c$.

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