(cos 780° - ctg495°)*sin225° Помогите.

Question

(cos 780° - ctg495°)*sin225°
Помогите.

Answer 1

[cos(720+60)-ctg(360+135)]*sin(180+45)=(cos60-ctg(180-45))*(-sin45)=
=(cos60+ctg45)*(-sin45)=(1/2+1)*(-√2/2)=-3√2/4