(1)sin378°21′=sin(360+18度21分）=sin18度21分
tan1111=tan(1080+31)=tan31>sin31
cos642.5=cos(720-77.5)=cos77.5=sin(90-77.5)=sin12.5
故tan1111>sin378 21 >cos642.5
(2)sin(-879)=sin(-1080+201)=sin201=sin(180+21)=-sin21
tan(-8/33pi)=-tan8/33pi=-tan43.6
cos(-10/13pi)=cos10/13pi=-cos(pi-3/13pi)=-cos3/13pi=-cos(pi/2-7/26pi)=-sin7/26pi=-sin48
故sin(-879)>cos(-10/13pi)>tan(-8/33pi)