sin120°= cos120°=

sin120°= 根号3/2 cos120°=-0.5
sin60°= 根号3/2 cos60°=0.5
sin150°= 0.5 cos150°=-根号3/2
sin30°= 0.5 cos30°=根号3/2
sin140°= 0.643 cos140°=-0.766
sin40°= 0.643 cos40°=0.766
（1）sin120°= sin60°,sin150°= sin30°,sin140°= sin40°
cos120°=- cos60°,cos150°=-cos30°,cos140°=-cos40°
2.
(1) sina (2)-cosa
(3)sin130°=sin50°=cos40° cos135°=- cos45°= - 根号2/2
∠A=150° or 30°