Problem
Write the expression as a single Runctiblt of a \[ \cos \left(90^{\circ}-a\right) \] Choose the corred answer below. A. $-\sin \alpha$ B. $-\cos \alpha$ C. $\sin \alpha$ D. $\cos \alpha$
Solution
Step 1 ：Write the expression as a single function of a: \(\cos (90^{\circ}-a)\)
Step 2 ：Choose the correct answer below.
Step 3 ：Final Answer: The correct answer is \(\boxed{\sin \alpha}\)
