Question Detail
Question
If cos a = 4/5, what is sin a in the first quadrant?
Correct Answer
Option A is the correct answer.
Detailed Explanation
Using sin² a + cos² a = 1, sin² a = 1 - (16/25) = 9/25, so sin a = 3/5 (positive in first quadrant).
Hint
The notes indicate answer A.