函數y=(12)-x2+x+2的單調遞增區間是:___.

函數y=(12)-x2+x+2的單調遞增區間是:___.


令t=-x2+x+2=-(x-2)(x+1)=-(x-12)2+ ;94,∴y=(12)t,32≥t≥0,-1≤x≤2,故t的减區間為[12,2],∴函數y的增區間為[12,2].



函數f(x)=sin(x+π/6)+sin(x+π/3)在哪個區間上單調遞增
A(-π/2,π/12)B(-π/3,π/12)C(π/2,π)D(-2/π,π)


∵y=sin(x+π/6)+sin(x+π/3)
=sinxcos(π/6)+cosxsin(π/6)+sinxcos(π/3)+cosxsin(π/3)
=(1/2+√3/2)sinx+(1/2+√3/2)cosx
=(1/2+√3/2)*√2[sinx*(√2/2)+cosx*(√2/2)]
=(1/2+√3/2)*√2[sinx*cos(π/4)+cosx*sin(π/4)]
=(1/2+√3/2)*√2sin(x+π/4)
∵y=sinx在(-π/2,π/2)上遞增
∴y=sin(x+π/4)在(-3π/4,π/4)上遞增
參攷選項,選B