Half-angle formulae
Trigonometric ratios and identities · Mathematics
Study notes
Q: Find sin 15° using the half-angle formula with A = 30°. sin²15° = (1 - cos30°)/2 = (1 - √3/2)/2 = (2-√3)/4. sin 15° = √(2-√3)/2 (positive, 15° in Q1). Numerically ≈ 0.2588.