Triple-angle formulae
Trigonometric ratios and identities · Mathematics
Study notes
Q: Express sin 3A and evaluate sin 3A when sin A = 1/2 (A = 30°). sin 3A = 3sinA - 4sin³A. With sin A = 1/2: 3(1/2) - 4(1/8) = 3/2 - 1/2 = 1. Check: 3A = 90°, sin 90° = 1. ✓