Решить уравнение: f (x) = 1,5sin2x-5sinx-x, если f'' (x) = 0

F' (x) = 1,5 (sin2x) ' - 5 (sinx) ' - x' = 3cos2x - 5cosx - 1

f'' (x) = 3 (cos2x) ' - 5 (cosx) ' - 1' = - 6sin2x + 5sinx = 0

5sinx - 6 (2sinxcosx) = 0

5sinx - 12sinxcosx = 0

sinx (5-12cosx) = 0

5-12cosx=0

12cosx=5

cosx=5/12=0.416

x = acos (0.416) = 65.4