A particle of mass is travelling along the x-axis with velocity . It collides elastically with a stationary particle of mass . After the collision, the particle of mass is travelling with speed at angle to the x-axis, and the particle of mass is travelling with speed at angle to the x-axis.

The conservation of momentum laws for this collision are:

(i)

(ii)

The conservation of energy equation is:

(iii)

I have to show that these 3 equations imply:

, where