The "Examples" section doesn't seem to talk about ratios, do you mean the end of the prior "Calculation" section? If so part is just saying you can calculate the ratio of r_a to r_p given you know e and run it through the equation, not that e itself = r_a / r_p (the formula to calculate e from r_a and r_p is higher up in the section).

If not that section, apologies for missing what you're trying to point out - I'm just trying to see what needs to be cleaned up so I can make an edit if needed.