tan(3x)=
问题描述：
tan(3x)=
答
sin3a=sin2acosa+cos2asina =2sinacosacosa+[1-2(sina)^2]sina =-4(sina)^3+3sina.cos3a=cos2acosa-sin2asina =[2(cosa)^2-1]cosa-2sinacosasina =4(cosa)^3-3cosa.tan3a=(tan2a+tana)/(1-tan2atana) =[2tana/(1-(ta...