Let $\displaystyle f(x)$ be a continuous function on the interval $\displaystyle [0,\pi].$If $\displaystyle \int_{0}^{\pi}f(x)\sin x dx=0$ and $\displaystyle \int_{0}^{\pi}f(x)\cos x dx=0$,then prove that $\displaystyle f(x)=0$ must have atleast two real roots on the interval $\displaystyle (0,\pi).$