Question

calcule f'(pi), sabendo que f(x)=3lnx+cosx

Answer 1

Olá, Paulim.

 

$<var> f(x)=3\ln x+\cos x\\\\ f'(x)=\frac3 x-\sin x\\\\ f'(\pi)=\frac3 \pi-\underbrace{\sin\pi}_{=0}\\\\\\ \therefore \boxed{f'(\pi)=\frac3 \pi}</var>$