sin(-879°)=-sin879°=-sin(2*360°+159°)=-sin(159°)=-sin(180°-21°)=-sin21° ；tan(-33π/8)=-tan(4π+π/8)=-tan(π/8)=-tan22.5°=-0.4142；cos(-13π/10)=cos(13π/10)=cos(π+3π/10)=-cos(3π/10)=-cos...