Найти множество значений функции y=3cos5x-7

y = 3 cos5x-7
y = cosx --> y = cos5x ---> y = 3cos5x ---> y = 3cos5x - 7

- 1 ≤ cosx ≤ 1
- 1 ≤ cos5x ≤ 1  /*3
 - 3 ≤ 3cos5x ≤ 3
- 3 - 7 ≤ 3cos5x - 7 ≤ 3 - 7
- 10 ≤ 3cos5x - 7 ≤  - 4

E (y) = [ - 10; - 4]