=cos²x+sinx
=1-sin²x+sinx
=-sin²x+sinx-1/4+1/4+1
=-(sinx-(1/2))²+(5/4)当|x|≤π/4,
-√2/2≤sinx≤√2/2∴当sinx=1/2时,
y有最大值,
y(max)=5/4,
此时,x=π/6当sinx=-√2/2时(离对称轴sinx=1/2最远),
y有最小值y(min)
=1-(1/2)+(-√2/2)
=(1-√2)/2,
此时,x=-π/4