Question

Обчислить: 

tg 330 = 

cos (- $frac{5 pi }{4}$) = 

Answer 1

$tg 330 = tg (360-30) = tg (-30) = -tg30=- frac{ sqrt{3} }{3} \ cos (- frac{5 pi }{4} ) =cos frac{5 pi }{4} =cos ( pi + frac{ pi }{4} ) =-cos frac{ pi }{4} =- frac{ sqrt{2} }{2}$