tan3π/5= tan(π-2π/5)=-tan2π/5,
tan100°21′=tan(180°-79°39′)=-tan79°39′
tan31π/36= tan(π-5π/36)=-tan5π/36
tan324°32′=tan(360°-35°28′)=-tan35°28′
cos65π/6=cos(60+5)π/6=cos5π/6=cos(π-π/6)=-cosπ/6=负的2分之根号3
sin（-31π/4）=sin（-32+1）π/4=sin（π/4）=2分之根号2
cos（-1182°13′）=cos（-1080°-102°13′）=cos（-102°13′）=cos102°13′=cos（180°-77°47′）=-cos77°47′
sin670°39′=sin720°-49°21′=-sin49°21′
tan（-26π/3）=tan（-24-2）π/3=tan-2π/3=-tan2π/3=-tan（π-π/3）=tanπ/3=根号3
tan580°21′=tan（720°-139°39′）=-tan（180°-40°21′）=tan40°21′