There could be many different correct answers, such as
- A radius of a circle is perpendicular to a chord if and only if it (bisects the minor arc)
- A radius of a circle is perpendicular to a chord if and only if it (bisects the major arc)
- A radius of a circle is perpendicular to a chord if and only if it (bisects the subtended angle of the chord)
- A radius of a circle is perpendicular to a chord if and only if it (bisects the chord)
There may be other ones!
