Question

Qual o cosseno de 165°(com a conta).

Answer 1

Cos165º=Cos(120+45):

Cos(120+45)=cos120.cos45-sen120.sen45
Cos(120+45)=-1/2.√2/2-√3/2.√2/2
Cos(120+45)=-√2/4-√6/4
Cos(120+45)=(-√2-√6)/4

Cos165º=-(√6+√2)/4