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maths2u.com/method.html
Why the pages look like this

The Method

A proof is only honest if it names its hypotheses and shows what each one is doing. Every page here is held to that.

Every hypothesis, with its role

Each hypothesis is paired with a counterexample showing what breaks without it — the maths analogue of a domain of validity.

Every step justified

One inference per line, each with its warrant. No "clearly", no "it follows that" without a reason.

Corollaries & converses

What the theorem gives for free, and whether it runs backwards.

Three tiers, in place

The idea in words, the standard proof, and the rigour a lecturer waves past — toggle depth without leaving the page.