Bragg and Van Laue diffraction

Bragg and Van Laue formulation are two approach for reaching to the same phenomenon. For a constructive interference K = k'-k must be reciprocal lattice vector with K = 2dsina = (2pi/d)n, where a is the angle between the incident ray and lattice plane. So we reach the Bragg condition which is 2dsina=n* wavelength of incident ray.