Question

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

Answer 1

f'(x)=-3sinx+4cosx-5
4cosx-3sinx=5
16cos^2x+9sin^2x-24sinxcosx=25sin^2x+25cos^2x
9cos^2x+16sin^2x+24sinxcosx=0
(3cosx+4sinx)^2=0
tgx=-3/4
x=-arctg(3/4)+Пk