Найти множество значений функции, методом оценки. Буду благодарен)

Y= sin(x-П/3)*sin(x+П/3)

Y = sin(x-π/3)•sin(x+π/3)

1)sin(x-π/3) = sinx•cos(π/3)-cos(x)•sin(π/3) = 1/2sinx - √3/2cosx

2)sin(x+π/3) = 1/2sinx + ✓3/2cosx

3)Y = 1/4sin²x + 3/4cos²x = 1/4sin²x+3/4(1-sin²x) = 1/4sin²x -3/4sin²x + 3/4 = -1/2sin²x + 3/4

4)

-1 <= sinx <= 1

0 <= sin² x <= 1|•(-1/2)

-1/2 <= -1/2sin²x <= 0|+3/4

1/4 <= -1/2sin²x + 3/4 <= 3/4

E(y): [1/4; 3/4]