Let \( A(6,8) \), \( B(10\cos\alpha,-10\sin\alpha) \) and \( C(-10\sin\alpha,10\cos\alpha) \), be the vertices of a triangle. If \( L(a,9) \) and \( G(h,k) \) be its orthocenter and centroid respectively, then \( (5a-3h+6k+100\sin 2\alpha )\) is equal to ____________.