If `cosy=xcos(a+y)` , with `cosa!=+-1` , prove that `(dy)/(dx)=(cos^2(a+y))/(sina)` .

Explanation

To prove that \(\frac{dy}{dx} = \frac{\cos^2(a+y)}{\sin a}\) given the equation \( \cos y = x \cos(a+y) \), we will follow these steps:

### Step 1: Differentiate both sides with respect to \(x\)

Starting with the equation:
\[ \cos y = x \cos(a+y) \]
...