Pion decay and photon frequencies

[snc1318]

Homework Statement

we are given a neutral pion moving at 0.98c straight in the x-direction. The pions rest mass is 135MeV/c^2. two photons are emitted in opposite direction parallel to the pion's motion.

I need to find the two frequencies of each photon.

Homework Equations

m=0, E=p*c
conservation of Energy E^2=(c*p)^2+(m*c^2)^2
gamma=1/sqrt(1-Beta^2)
Beta = v/c
p=gamma*m*v
E=gamma*m*c^2

The Attempt at a Solution

i know that energy and momentum are conserved but i don't know exactly what i am meant to do with the momentum relation of each pion. i keep trying all different tactics but keep going in circles. i feel like I am missing something really obvious.

 

[kuruman]

If you don't show what you have done, we cannot diagnose where you went wrong. You have two equations (momentum and energy conservation) and two unknown photon frequencies. Begin by writing

P_before=P_after
E_before=E_after