求函數y=sin(x+π/6)+cosx,(0≤x≤π)的最大值和最小值

求函數y=sin(x+π/6)+cosx,(0≤x≤π)的最大值和最小值

y=sin(x+π/6)+cosx
=sinxcos(π/6)+cosxsin(π/6)+cosx
=(√3/2)*sinx+(3/2)cosx
=√3*[(1/2)*sinx+(√3/2)cosx]
=√3*sin(x+π/3)
因為0≤x≤π,即π/3≤x+π/3≤4π/3
所以-√3/2≤sin(x+π/3)≤1
則當x+π/3=π/2,即x=π/6時,sin(x+π/3)=1,函數y有最大值√3;
當x+π/3=4π/3,即x=π時,sin(x+π/3)=-√3/2,函數y有最小值-3/2.