f(a)=[sin(TT-a)cos(2TT-a)tan(-a-TT)]/[sin(-a-TT)]
=[sin(a)cos(-a)tan(-a)]/[sin(-a)]
=[sin(a)cos(a)*-tan(a)]/[-sin(a)]
=[sin(a)^2]/[sin(a)]
=sina
ps:一般用pi,很少用TT...若a是第三象限角，且sin[a-(3TT)/2]=-5/13，求f(a)的值sin[a-(3TT)/2] = sin(a+pi/2) = cosa = -5/13sin a = -12/13f(a) = -12/13