Question Detail
Question
If sin a = 3/5 and a is in the first quadrant, what is cos a?
Correct Answer
Option A is the correct answer.
Detailed Explanation
Using sin² a + cos² a = 1, (3/5)² + cos² a = 1, so cos² a = 1 - 9/25 = 16/25, thus cos a = 4/5 (positive in first quadrant).
Hint
The notes indicate answer A.