Question

Calculati cos 60 grade cos 30 grade + sin 60 grade sin 30 grade.
Ce se pune intre cos 60 grade cos 30 grade ( de exemplu ) ?

Answer 1

Pai sa consideram x=60 si y=30
cosx*cosy+sinx*siny=cos(x-y)
Deci, in cazul tau, cos 60*cos 30+sin 60*sin30=cos(60-30)=cos30= $\frac{ \sqrt{3} }{2}$