Suppose *X* is a circle,
is any diameter of the circle, and
is any chord of the circle.
Then
bisects
if and only if
is perpendicular to .
``If and only if'' means *both* of the following statements are true:
If bisects
then
is perpendicular to .
If
is perpendicular to
then
bisects .

chorddiam.eps

Wed Apr 21 08:17:28 EDT 1999