sin18°+sin20°

sin18° + sin20° can be simplified using the sum-to-product identity: sin a + sin b = 2 sin((a+b)/2) cos((a−b)/2).

Let a = 18°, b = 20°: sin18° + sin20° = 2 sin(19°) cos(1°) ≈ 2 × 0.325568 × 0.999848 ≈ 0.651037.

Numerically, sin18° ≈ 0.30901699 and sin20° ≈ 0.34202014, so the sum is ≈ 0.65103714.

If you want a compact exact form: sin18° + sin20° = 2 sin(19°) cos(1°).