f(x)=3sin(x-20°)+5sin(x+40°)的最大值
问题描述：
f(x)=3sin(x-20°)+5sin(x+40°)的最大值
答
x-20°=x+40°-60°所以,sin(x-20°)=sin[(x+40°)-60°]=(1/2)sin(x+40°)-(√3/2)cos(x+40°)所以,f(x)=(3/2)sin(x+40°)-(3√3/2)cos(x+40°)+5sin(x+40°)=(13/2)sin(x+40°)-(3√3/2)cos(x+40°)=7sin[(x+40°)...