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Proof by modus tollens

To provep =>q we prove [(~q) A{p =>q)] =H,~p) instead.

Example:

We know, that if a right triangle has sides of lengths a, b, c, which c is the largest, then a2 + b2 = c2 (j? =łq). Therefore, if we prove that for any triangle with sides of lengths x, y, z, where z is the largest, it is not true, that x2 + y2 = z2 (x2 + y2 6= z2), we may conclude - by modus tollens - that this is not a right triangle.