Question

求下列三角函数值cos225°sin11/3πsin(-16/3π)cos(-2040°)

Answer 1

cos225°=cos(-225°)=cos(360°-225°)=cos135°=-√2/2

sin11/3π=cos(4π-1/3π)=cos(-1/3π)=cos1/3π=1/2

sin(-16/3π)=sin(-6π+2/3π)=sin2/3π=sin(π-1/3π)=sin1/3π=√3/2

cos(-2040°)=cos(-6*360°+120°)=cos120°=-1/2