Answer:
Radii
Explanation:
Circle is a geometric shape with centre at the middle and all points on the circumference keeping equal distance from the centre
Circle has so many theorems
Tangent segment theorem is the theorem about tangents.
Arc length theorem is for arc.
Chord is perpendicular to the line joining mid point of the chord and centre is one of the theorems on chords
Thus we have so many theorems for tangents,chords and arcs of a circle.
But for radii no theorem is there.