Answer: 2sinA cosA.
- A sin²A + cos²A
- B 2sinA
- C 2sinA cosA
- D sin²A - cos²A
Correct answer: C. 2sinA cosA
Explanation: Double angle formula: sin 2A = 2 sinA cosA.
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