若f(a)=(2tana)-[(2sin^2a/2 -1)/sin(a/2)cos(a/2)]则f(兀/12)=

问题描述:

若f(a)=(2tana)-[(2sin^2a/2 -1)/sin(a/2)cos(a/2)]则f(兀/12)=

由f(a)=(2tana)-[(2sin^2a/2 -1)/sin(a/2)cos(a/2)]先对f(a)进行化简f(a)=(2tana)-[-2(1-2sin^2a/2 )/2sin(a/2)cos(a/2)] =(2tana)+2cosa/sina =2(sina/cosa+cosa/sina) =2[(sin^2a+cos^2a)/sinacosa...