f(a)= 2 tana-[2(sina/2)^2-1]/[(sina/2)(cosa/2)],求f(π/12)
问题描述：
f(a)= 2 tana-[2(sina/2)^2-1]/[(sina/2)(cosa/2)],求f(π/12)
答
f(a)= 2 tana-[2(sina/2)^2-1]/[(sina/2)(cosa/2)]=2tana+cosa/(1/2sina)=2(tana+cota)=2(sina/cosa+cosa/sina)=2(sin^2a+cos^2a)/(sinacosa)=4/sin(2a)f(π/12)=4/sin(π/6)=8