Answer
$$\cot\alpha\sin\alpha=\cos\alpha$$
Work Step by Step
$$A=\cot\alpha\sin\alpha$$
- Quotient Identity: $$\cot\alpha=\frac{\cos\alpha}{\sin\alpha}$$
That makes $A$ into $$A=\frac{\cos\alpha}{\sin\alpha}\times\sin\alpha$$
$$A=\cos\alpha$$