Differential Equations

If \(y = y(x),y \in \left[ {0,{\pi \over 2}} \right)\) is the solution of the differential equation \(\sec y{{dy} \over {dx}} - \sin (x + y) - \sin (x - y) = 0\), with y(0) = 0, then \(5y'\left( {{\pi \over 2}} \right)\) is equal to ______________.