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

f'(x)= - 3sinx + 4cosx - 54 cosx - 3sinx = 516cos^2x - 24sinxcosx + 9sin^2x = 25*116cos^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 = 03cosx + 4sinx = 0   /:cosx ≠ 04tgx + 3 = 0 4tgx = - 3tgx= - 3/4x= - arctg(3/4)  + pik, k ∈Z