Решите уравнение f'(x)=0 f(x)=3cosx+4sinx-5x

f'(x)= - 3sinx + 4cosx - 5 4 cosx - 3sinx = 5 16cos^2x - 24sinxcosx + 9sin^2x = 25*1 16cos^2x - 24sinxcosx + 9sin^2x = 25*(sin^2x + cos^2x)  16cos^2x - 24sinxcosx + 9sin^2x  = 25sin^2x + 25cos^2x - 9cos^2x - 24sinxcosx - 16 sin^2x  = 0  /:(-1) 9cos^2x + 24sinxcosx + 16sin^2x = 0 (3cosx + 4sinx)^2 = 0 3cosx + 4sinx = 0   /:cosx ≠ 0 4tgx + 3 = 0  4tgx = - 3 tgx= - 3/4 x= - arctg(3/4)  + pik, k ∈Z