If two circles touch one another externally then the (straight line) joining their centers will go through the point of union. * For let two circles, $ABC$ and $ADE$, touch one another externally at point $A$, and let the center $F$ of $ABC$ have been found [Prop. 3.1], and (the center) $G$ of $ADE$ [Prop. 3.1]. * I say that the straight line joining $F$ to $G$ will go through the point of union at $A$.
If two circles touch one another externally at a point $A$, then the straight line going through their centers goes also through $A$.
Proofs: 1
Sections: 1