Simplify Trig Expression
1. The problem is to simplify the expression $$\frac{\cos A}{1-\tan A} + \frac{\sin A}{1-\cot A}$$.
2. Recall that $$\tan A = \frac{\sin A}{\cos A}$$ and $$\cot A = \frac{\cos A}{\sin A}$$.
3. Substitute these into the expression:
$$\frac{\cos A}{1 - \frac{\sin A}{\cos A}} + \frac{\sin A}{1- \frac{\cos A}{\sin A}}$$.
4. Simplify the denominators:
$$1 - \frac{\sin A}{\cos A} = \frac{\cos A - \sin A}{\cos A}$$,
$$1 - \frac{\cos A}{\sin A} = \frac{\sin A - \cos A}{\sin A}$$.
5. Rewrite the original expression with these:
$$\frac{\cos A}{\frac{\cos A - \sin A}{\cos A}} + \frac{\sin A}{\frac{\sin A - \cos A}{\sin A}} = \frac{\cos A \cdot \cos A}{\cos A - \sin A} + \frac{\sin A \cdot \sin A}{\sin A - \cos A}$$.
6. This becomes:
$$\frac{\cos^2 A}{\cos A - \sin A} + \frac{\sin^2 A}{\sin A - \cos A}$$.
7. Note that $$\sin A - \cos A = -(\cos A - \sin A)$$, so rewrite second term:
$$\frac{\cos^2 A}{\cos A - \sin A} - \frac{\sin^2 A}{\cos A - \sin A} = \frac{\cos^2 A - \sin^2 A}{\cos A - \sin A}$$.
8. Recognize numerator as $$\cos 2A$$ identity:
$$\cos^2 A - \sin^2 A = \cos 2A$$.
9. The expression now is:
$$\frac{\cos 2A}{\cos A - \sin A}$$.
**Final answer:** $$\frac{\cos 2A}{\cos A - \sin A}$$.