Решение
1. sin20°cos40° + cos20°sin40° = sin(20° + 40°) = sin60° = √31/2)*(/2
2. Вычислите синус углов: 75 градусов; 105 градусов
sin75° = sin(30° + 45°) = sin30°cos45° + cos30°sin45° =
= (1/2)*(√2/2) = √2/4
sin105° = sin(60° + 45°) = sin60°cos45° + cos60°sin45° =
= (√3/2)*(√2/2) + (1/2)*(√2/2) = √6/4 + √2/4 = (√6 + √2)/4