Вычислите : 1) sin30° cos60° - sin²45 ° 2) 2cos180° - вопрос №692021413060452218027033060 от Chempionsyper 08.05.2020 20:28

Question

Геометрия: Вычислите : 1) sin30° cos60° - sin²45 ° 2) 2cos180° - sin²270° 3) cos30° sin60° + cos² 45° 4) 3sin 90° - cos² 0°

Chempionsyper · Answer

1) sin30° cos60° - sin²45° = 1/2•1/2 - 1/2 = -1/4
2) 2cos180° - sin²270° = 2•(-1) - 1 = -3
3) cos30° sin60° + cos² 45° = 1/2•1/2 + 1/2 = 1/4 + 1/2 = 3/4.
4) 3sin 90° - cos² 0° = 3•1 - 1 = 2.