Hi, I've attached a file displaying a derivation to make the kinetic energy of a two-body problem into a kinetic energy only involving the reduced mass. When plugging 8.3 into 8.1, I just don't quite see how this derivation makes sense. Shouldn't there be a $$ \mu^2$$ term? Since when squaring the absolute value of r1, aren't the mass terms also squared? If I'm not mistaken, it simply looks like the mass terms are not squared when plugging in 8.3 into 8.1. I feel like I'm missing something painfully obvious here, so any help is appreciated!