In a circle, equal straight lines are equally far from the center, and (straight lines) which are equally far from the center are equal to one another. * Let $ABDC$^{1} be a circle, and let $AB$ and $CD$ be equal straight lines within it. * I say that $AB$ and $CD$ are equally far from the center.
Two chords in a circle are equal in length if and only if they are equally far from the center of the circle.
Proofs: 1
Proofs: 1
The Greek text has "$ABCD$", which is obviously a mistake (translator's note). ↩