f(a)=sin(pi-a)cos(2pi-a)tan(-a+3pi/2)/cos(-pi-a) 求 f(-31pi/3)的值

问题描述:

f(a)=sin(pi-a)cos(2pi-a)tan(-a+3pi/2)/cos(-pi-a) 求 f(-31pi/3)的值

f(a)=sin(pi-a)cos(2pi-a)tan(-a+3pi/2)/cos(-pi-a)
=sinacosacota/cosa
= cosa
f(-31pi/3)=cos(-31pi/3)=cos(31pi/3)=cos(10pi+pi/3)=cos(pi/3)=1/2