MCQ
यदि $\sin y=x \cos (a+y)$, तब $\frac{d x}{d y}$ है-
  • $\frac{\cos a}{\cos ^2(a+y)}$
  • B
    $\frac{-\cos a}{\cos ^2(a+y)}$
  • C
    $\frac{\cos a}{\sin ^2 y}$
  • D
    $\frac{-\cos a}{\sin ^2 y}$

Answer

Correct option: A.
$\frac{\cos a}{\cos ^2(a+y)}$
(A) $\frac{\cos a}{\cos ^2(a+y)}$
$\begin{aligned} \text  x & =\frac{\sin y}{\cos (a+y)} \\ \therefore \quad \frac{d x}{d y} & =\frac{\cos (a+y) \cos y-\sin y[-\sin (a+y)}{\cos ^2(x \times y)} \\ & =\frac{\cos (a+y) \cos y+\sin (a+y) \sin y}{\cos ^2(a+y)}\end{aligned}$
$=\frac{\cos (a+y-y)}{\cos ^2(a+y)}=\frac{\cos y}{\cos ^2(a+y)}$

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