Book VI.
PROP. XXVIII. and XXIX.

These two problems, to the first of which the 27th prop, is necessary,
are the most general and useful of all in the elements, and are most frequently made use of by the antient geometers in the solution of other problems;
and therefore are very ignorantly left out by Tacquet and Dechales in their editions of the elements, who pretend that they are
scarce of any use.





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