5
Answer: BSet 1: Trigonometry (Advanced)
Explanation
PROBLEM
If sin(theta) = 3/5 and theta is in the first quadrant, find cos(theta).
If sin(theta) = 3/5 and theta is in the first quadrant, find cos(theta).
A.
5/4
B.✓ Correct
4/5
C.
3/5
D.
3/4
Detailed Explanation
Choice B is the best answer. cos squared = 1 - sin squared = 1 - 9/25 = 16/25. cos = 4/5
Why others are wrong:
A: 5/4 is incorrect because it does not satisfy the equation.
C: 3/5 is incorrect because it does not satisfy the equation.
D: 3/4 is incorrect because it does not satisfy the equation.