\left\{2sinxcosx \right\} = \left\{sin2x \right\}....x - \left[x \right] = \left\{x \right\}
since in the interval ( 0 , π/4 ) ..{sin2x} varies b/w 0 to 1 ...so the integral can be written as
\int_{0}^{\pi /4}{\left\{sin2x \right\}d\left\{x \right\}} = \int_{0}^{1}{tdt} = \frac{t^{2}}{2} = \frac{1}{2}
please correct me if i am wrong