1、sin750° =sin(720 °+30 °)=sin30°=1/2
2、cos 22π/3 =cos(8π-2π/3)=cos2π/3=-1/2
3、tan（-7Π/4）=tan(-2π+π/4)=tanπ/4=1
4、 sin900°=sin(720 °+180 °)=sin180 °=0