If a point be taken within a circle, and more than two equal straight lines fall from the point on the circle, the point taken is the centre of the circle.
Si in circulo intus punctum signetur a quo linee plures duabus ad lineam circumductam ducantur fuerintque linee equales, punctum predictum centrum est circuli.
SI in circulo acceptum fuerit punctum aliquod, & ab eo puncto ad circulum cadant plures, quam duæ, rectæ lineæ æquales; acceptum punctum centrum est ipsius circuli.
Title
Book I
