Answer: cos θ.
- A sin θ
- B cos θ
- C -sin θ
- D -cos θ
Correct answer: B. cos θ
Explanation: sin(90° - θ) = cos θ. 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