Let In=∫0π/2 xncos⁡ x dx then I8+56I6  is equal to

In=∫0π/2 xncos⁡ xdx=xnsin⁡ x0π/2−n∫0π/2 xn−1sin⁡ xdx=π2n−n−xn−1cos⁡ x0π/2+(n−1)∫0π/2 xn−2cos⁡ xdx=π2n−n(n−1)In−2I8+8.7I6=π28