Предмет: Алгебра, автор: 21blackcat12

1.Упростить:
а) sin(5п/2+a); б) cos(3п/2+a); в) sin(7п/2-a)
2. Вычислить: 3cos(7п/2+a) +2 sin(17п-a), если sin a = -0,2.
3. Доказать равенство:
3cos 50-4sin140 делённое на cos 130 = 1.
С решением, пожалуйста, не просто ответ

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Автор ответа: okneret

Применены формулы приведения

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