Given: \[ \tan A = \frac{x}{y} \Rightarrow \frac{\sin A}{\cos A} = \frac{x}{y} \Rightarrow \frac{\cos A}{\sin A} = \frac{y}{x} \] Now, using the identity and applying the componendo-dividendo rule: \[ \frac{\cos A + \sin A}{\cos A - \sin A} = \frac{y + x}{y - x} \Rightarrow \frac{\cos A - \sin A}{\cos A + \sin A} = \frac{y - x}{y + x} \] (Answer)