Relativity and energy (think its dead easy, I just can't see it)

[Brewer]

Homework Statement

A proton has total energy 2GeV and is traveling along the x-axis. A photon with energy 50MeV travels at an angle of 45 degrees to this axis. What is the total energy and momentum of the system?

Homework Equations

Non-really

The Attempt at a Solution

Total E = 2Gev + 50 MeV = 2.05GeV yes? I don't need to take any directions into account here do I?

Then px = p(proton) + px(photon), and py = py(photon) yes?

 

[Dick]

Yes, that's it.