三角恒等变换公式转换22tantan 2 =1tantantantan()1tantan 2222cos2 =cossin=2cos1=1 2sinsin 2 =2sincos SSCC ()()()()221 cos =2cos 21 cos =2sin 21sincos =sin()sin()]21cossin =sin()sin()]21coscos =cos()cos()]21sinsin =cos()cos()]2 [[[[1 cossin 221 coscos 221 cossin1 costan==21 cos1 cossinABABsin Asin B=2sincos22ABABsin Asin B=2cossin22ABABcosAcosB=2coscos22ABABcosAcosB=2sinsin22相除相除变形相除相加减移项,2 令AB