y=36tgx-36x+9π-4

1) ооф: x - любое число

2) y' = 36 / cos^2(x) - 36 = (36 - 36cos^2(x)) / cos^2(x)

3) y' = 0 => 36 - 36cos^2(x) = 0

-cos^2(x)=-1

cosx = 1 => x = 2πn - не принадлежит [-π/4;π/4]

cosx = -1 => x = π + 2πn - не принадлежит [-π/4;π/4]

4) y(-π/4) = 36tg(-π/4) - 36(-π/4) + 9π - 4 = -36 + 9π + 9π + 4 = -32 + 18π

y(π/4) = 36tg(π/4) - 36(π/4) + 9π - 4 = 36 - 9π + 9π + 4 = 40

Ответ: 40.