1. The problem statement, all variables and given/known data I'm working on this problem here: http://hyperphysics.phy-astr.gsu.edu/hbase/astro/redshf2.html The answer is already listed, it's the steps I'm worried about. I don't see how they get from step 1 to step 2 here. They don't even tell me what T is. It seems that they are substitution T into the equation. I would think T = lambda/c+v but that's not what they're doing here. I can't get from step 2 to 3, nor 3 to 4. They don't tell you what the equation for lambda source is, so I don't see how they work that into the equation. Beta = v/c Well if that's true then (1+v/c)^2 = 1 + 2v/c + (v/c)^2 not what they have.