Cutting from a sharp-angled triangle a part equal to an obtuse one
Removing triangle m o p toward the point of acute triangle a b c
Leonardo wants to cut off, toward the point of a very acute triangle a b c, an area equal to a given obtuse triangle m o p of unknown size. He lays m o p as a f g between parallels a distance f K apart, then draws the line g n where the parallel e d meets side a b, obtaining triangle a g n equal to a g f and cut from a b c. The top of the page carries a tall narrow acute triangle with internal construction lines beside a low, wide obtuse triangle labelled o, q, m.
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Removing an obtuse-triangle area from a sharp triangle
From the very acute triangle a b c Leonardo removes, toward its point, an area equal to the given obtuse triangle m o p. He sets m o p as a f g between parallels at distance f K, then, where the parallel e d cuts side a b, draws g n to make triangle a g n equal to a g f, which is thereby cut from a b c.