f(x)=cos2x+2sinx=1-2(six)^2+2sinx=-2(sinx-1/2)^2+3/2这一步怎么来的想不通_数学解答

f(x)=cos2x+2sinx=1-2(six)^2+2sinx=-2(sinx-1/2)^2+3/2这一步怎么来的想不通

人气：487 ℃　时间：2020-06-10 07:40:21

解答

f(x)=cos2x+2sinx
=1-2(sinx)^2 +2sinx
=-2(sinx)^2 +2sinx+1
=-2[(sin)^2-sinx]+1
=-2[(sin)^2-sinx+1/4-1/4]+1
=-2[(sin)^2-sinx+1/4]++1/2+1
=-2(sinx-1/2)^2+3/2