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Just getting back here Hmm, I don’t rbemmeer what I did when I looked at this before. I’m sure it’s on a scrap of paper at my house in California, but I’m in Michigan for the holidays. I just thought it through again and That line (We can take the derivative of both sides as many times as we want to see that f^{(i)}(\pi x) = f^{(i)}(x) for any i, as well.) makes perfect sense to me now. If two functions are equal (for all values of the variable), I’d guess their derivatives must be equal. I have a few questions still:What does it mean to take the derivative of f(pi-x)? Are we talking about df/dx or df/d(pi-x)? (Your last comment isn’t making sense to me, and I thought this might be where I’m not following you.)Calling f a’ function, when it depends on values of n, is still bothering me. Does it work to think of this as a collection of functions, where f sub n is as you gave f?You mentioned on your previous post that you’d be interested in working through other interesting proofs. Sam Shah just mentioned the on his blog. That’s something I’ve always been intrigued by, and never learned the proof of.This is something that never would have happened before the internet. I appreciate the opportunity to learn more mathematics.