§ 23: 23.2

23.2 Спростіть вираз:

1) cos(6α + 2α) = cos8α;

2) sin75°cos15° – sin15°cos75° = sin60° = 32;

3) cos⁡(64°-4°)sin⁡(19°+41°) = cos60°sin60° = ctg60° = 33;

4) cosαcosβ + sinαsinβ – 2sinαsinβ = cosαcosβ – sinαsinβ = cos(α + β).