sin(pi)=sin(180°)=0,
sin(pi/2)=sin(90°)=1,
sin(pi/4))=sin(45°)=(根号2)/2=0.707,
cos(pi)=cos(180°)=-1,
cos(pi/2)=cos(90°)=0,
cos(pi/4))=cos(45°)=(根号2)/2=0.707,
tan(pi)=tan(180°)=0,
tan(pi/2)=tan(90°)=无穷大,
tan(pi/4))=tan(45°）=1,
cot(pi)=cot(180°)=无穷大,
cot(pi/2)=cot(90°)=0,
cot(pi/4))=cot(45°）=1,
sec(pi)=sec(180°)=-1,
sec(pi/2)=sec(90°)=0,
sec(pi/4))=sec(45°)=(根号2)/2=0.707,
csc(pi)=csc(180°)=0,
csc(pi/2)=csc(90°)=1,
csc(pi/4))=csc(45°)=(根号2)/2=0.707,