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BOOK I. PROP. III. PROB.
3
ROM the greater (
) of two given straight lines, to cut off a part equal to the less (
).
Draw 
= (pr. 2.); describe 
(post. 3.), then = 
.
For = (def. 15.),
and = (const.);
∴ = (ax. 1.).
Q.E.D.
