Cos150+Sin210+Cos1470+Cos(-570)
=Cos(∏-30)+Sin(3∏/2-60)+Cos(8∏+30)+Cos(-3∏-30)
通过诱导公式可再化为:
-Cos30+Cos60+Cos30-Cos30
=Cos60-Cos30
=(1-√3)/2
Cos150+Sin210+Cos1470+Cos(-570)
=Cos(∏-30)+Sin(3∏/2-60)+Cos(8∏+30)+Cos(-3∏-30)
通过诱导公式可再化为:
-Cos30+Cos60+Cos30-Cos30
=Cos60-Cos30
=(1-√3)/2