theartofproof.com is a website that is committed to providing rigorous math proofs.

Currently, they offer introductory number theory (proofs about the integers, rationals, natural numbers), but they will be expanding to the abstract algebra level and higher

Everything is provided in mathematical typeset so that the proofs are easy to follow and the proofs link to each other if referenced or mentioned

Under "Complete List of Proofs" you can see everything they currently offer. Check back often as it gets updated weekly

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Using elementary concubinary logic, you can easily show that the flumex is both semi-dependent and, even more importantly, quasi-invariant