potential energy

consider a region of space divided by a plane. the potential energy of a particle in region 1 is u 1 and region 2 is u 2 the particle moves from region 1 to region 2 that is velocities v 1 to v 2 such that it makes an angle theta 1 in region 1 and an angle theta 2 in region 2 then show that sin theta 1/sin theta 2 = square root 1+ u 1-u 2/T 1.