答案是:1. -2; 2. -(√3+3)/2
你应该知道三角函数都是周期函数,就是说tan(a+kπ) = tan(a),cos(a+2kπ) = cos(a),sin(a+2kπ) = sin(a)。而弧度制中的2π就是角度制中的360°。
cos(70π/3)=cos(72π/3 - 2π/3)=cos(24π - 2π/3)=cos(- 2π/3)=-1/2
tan(31π/4)=tan(32π/4-π/4)=tan(8π-π/4)=tan(-π/4)=-1
sin(29π/6)=sin(24π/6+5π/6)=sin(4π+5π/6)=sin(5π/6)=1/2
-1/2-1-1/2=-2
2.
cos(690°)=cos(720°-30°)=cos(-30°)=- √3/2
sin(1110)=sin(1080+30)=sin(30)=1/2
tan(-7π/4)=tan(8π/4-π/4)=tan(-π/4)=-1
- √3/2+1/2-1 = -(√3-3)/2