y=cosX+cos(X+60°)求值域 =cosx(1+cos60)-sinxsin60 =3/2cosx-√3/2sinx =√3cos(x+30) -√3<=Y<=√3 问题补充：y=sinaxsina(60°-x) 2y=cos(ax-60a+xa)-cos(ax+60a-ax) =cos(2ax-60a)-cos60a (-1-cos60a)/2<=y<=(1-cos60a)/2
y=cosX+cos(X+60°)=cosX+1/2cosX-√3/2sinX=3/2cosX--√3/2sinX =-√3cos(X-p),-1<=cos(X-p)<=1,--√3<=y<=√3.
cosx+cos(x+60)=cosx+cosxcos60-sinxsin60=3/2cosx-√3/2sinx =√3（√3/2cosx-1/2sinx)=√3sin(60-x) 所以值域为[-√3，√3），注：√为根号，60后面少写了度，这样清楚点
答：y=sin(x+45°)cos(x+45°)-1 =(1/2)*[2sin(x+45°)cos(x+45°)]-1 =(1/2)*sin[2(x+45°)]-1...详情>>
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