## A proof suggested by Pappus' Theorem

This proof is #42 in Loomis's book.
It is essentially the classical argument used to
prove Pappus' generalization of
Pythagoras' Theorem (p. 366 of
Heath, p. 126 of Loomis).
It is suggested in Howard Eves' book
**In Mathematical Circles** (published by Prindle,
Weber, and Schmidt, 1969), p. 74 and especially
the pictures on p. 75 that
it would make a good animation.
This is the earliest reference I am aware of where the idea
of an animated proof occurs.

Like many proofs, including Euclid's own, it partitions the
square on the hypotenuse by dropping a perpendicular
from the right angle through it. Then it performs
a sequence of shears and translations
to show corresponding areas are equal.

*Click on the figure to start an animation, to pause it
in the middle of an animation,
or to reset it to its initial configuration
if it is finished.*

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