sin(2乘2a)化简

题目

sin(2乘2a)化简

答案

sin(2×2a )=sin4a=2sin(2a)×2cos(2a)
sin(2a)=2sina×cosa
cos(2a)=1-2sin^2(a)=2cos^2(a)-1=cos^2(a)-sin^2(a)
后面的自己应该会化简了吧