$$ \int_0^{\pi / 2} \frac{\sin ^2 x}{\sin x+\cos x} d x= $$

[.] is the greatest integer function, then

$$ \int_0^{2 \pi}[|\sin x|+|\cos x|] d x= $$

If $f$ is defined on $R$ such that $f(x) f(-x)=9$, then $$ \int_{-23}^{23} \frac{d x}{3+f(x)}= $$