Set 3: Trigonometry (Advanced)

[Variation 1] **Choice B is the best answer.** cos squared = 1 - sin squared = 1 - 25/169 = 144/169. cos = 12/13

Explanation

Answer: B

PROBLEM

Recent studies show that if sin(theta) = 5/13 and theta is in the first quadrant, find cos(theta).

If sin(theta) = 5/13 and theta is in the first quadrant, find cos(theta).

5/12

12/13

✓ Correct

5/13

13/12

Detailed Explanation

[Variation 1] Choice B is the best answer. cos squared = 1 - sin squared = 1 - 25/169 = 144/169. cos = 12/13

Why others are wrong:

A: 5/12 is incorrect because it does not satisfy the equation.

C: 5/13 is incorrect because it does not satisfy the equation.

D: 13/12 is incorrect because it does not satisfy the equation.