Question

Помогите решить.Вычислите :
1)tg225 2)cos120 3)150

Answer 1

$1)tg(180^{o}+ alpha)= tgalpha$

$tg225^{o}= tg(180^{o}+45 ^{o})= tg45^{o}=1$

$2)cos(180^{o}- alpha)=-cosalpha$

$cos120^{o}=cos(180 ^{o}-60 ^{o})=- cos60^{o}=- frac{1}{2}$

$3)ctg(180^{o}- alpha)=-ctgalpha$

$ctg150^{o}=ctg(180^{o}-30 ^{o})=-ctg30 ^{o}=- sqrt{3}$