Question

这个式子第一步到第二步是怎么来的呢？

Answer 1

公式1：sinx=2sin(x/2)cos(x/2)证明:由sin(a+b)=sina*cosb+cosa*sinb可得：sinx=sin[(x/2)+(x/2)]=sin(x/2)cos(x/2)+cos(x/2)sin(x/2)=2sin(x/2)cos(x/2)公式2：cosx=2cos^2(x/2)-1证明:由cos(a+b)=cosa*cosb-sina*sinb可得：cosx=cos[(x/2)+(x/2)]=cos^2(x/2)-sin^x(x-2)=cos^2(x/2)-[1-cos^2(x/2]=2cos^2(x/2)-1。【结合公式cos^2(x/2)+sin^2(x/2)=1】所以f(x)=根号3*[2sin(x/2)cos(x/2)]-[2cos^2(x/2)-1]-1=第二步~

Answer 2

代入y=kx+1展开即得