Nếu \(\int\limits_0^\pi {f\left( x \right)\sin xdx} = 20,\int\limits_0^\pi {x.f'\left( x \right)\sin xdx} = 5\) thì \(\int\limits_0^{{\pi ^2}} {f\left( {\sqrt x } \right)\cos \sqrt x dx} \) bằng