Show that T1/T0 can be expressed in terms of m2/m1 ≡ a and cos ψ ≡ y

Question:

Show that T1/T0 can be expressed in terms of m2/m1 ≡ a and cos ψ ≡ y as

DIN

Plot T1/T0 as a function of ψ for a = 1, 2, 4, and 12. These plots correspond to the energies of protons or neutrons after scattering from hydrogen (a = 1), deuterium (a = 2), helium (a = 4) and carbon (a = 12), or of alpha particles scattered from helium (a = 1), oxygen (a = 4) and so forth.