Найдите значения выражений (подробно!!)

1) cos135°=cos(90°+45°)=-sin45°= - √2/2 2) sin(8π/3)=sin(3π -π/3)=sin(π/3)=√3/2 3) tg(7π/3)=tg(2π + π/3)=tg(π/3)=√3 4) cos(2 * π/8) = cos(π/4)=√2/2