3分之5π=300度,就是-60度,sin(-60)=-sin60=-根号3/2 cos-60=cos60=1/2,tan-60=-tan60=-根号3
sin(5π/3)=sin(2π/3+π)=-sin(2π/3)=-根号3除以2cos(5π/3)=cos(2π/3+π)=-cos(2π/3)=-1/2tan(5π/3)=tan(2π/3+π)=tan(2π/3)=-根号3
sin(5π/3)=sin(6π/3-π/3)=-sin(π/3)=-√3/2cos(5π/3)=cos(6π/3-π/3)=cos(π/3)=1/2tan(5π/3)=tan(6π/3-π/3)=-tan(π/3)=√3