Set 1: Trigonometry (Advanced)

**Choice B is the best answer.** cos squared = 1 - sin squared = 1 - 64/289 = 225/289. cos = 15/17

Explanation

Answer: B

PROBLEM

If sin(theta) = 8/17 and theta is in the first quadrant, find cos(theta).

17/15

15/17

✓ Correct

8/17

8/15

Detailed Explanation

Choice B is the best answer. cos squared = 1 - sin squared = 1 - 64/289 = 225/289. cos = 15/17

Why others are wrong:

A: 17/15 is incorrect because it does not satisfy the equation.

C: 8/17 is incorrect because it does not satisfy the equation.

D: 8/15 is incorrect because it does not satisfy the equation.