函數y=sin(x+β)(0≤β≤π)是R上的偶函數,求β的值?

函數y=sin(x+β)(0≤β≤π)是R上的偶函數,求β的值?

y=sin(x+β)=cos[π/2-(x+β)]=cos(x+β-π/2)
(0≤β≤π)是R上的偶函數,β-π/2=0
β=π/2