Answer: cosθ.
- A sinθ
- B -sinθ
- C cosθ
- D -cosθ
Correct answer: C. cosθ
Explanation: sin(90°+θ) = cosθ (complementary angle identity).
Unit circle with standard angles 0, 30, 45, 60, 90 degrees; at 45 degrees the point is (cos45, sin45) = (1/sqrt2, 1/sqrt2).
Concept context
Ratios, identities, and applications in triangles