Question

Вычислите:
cos(270+60)+cos(180-60)

Answer 1

cos330+cos120=$sqrt{3}$
cos120=cos(180-60)=-cos60=-1/2 
cos(360-30) = cos30 = $frac{ sqrt{3} }{2}$
$- frac{1}{2} + frac{ sqrt{3} }{2}= sqrt{3}$