Circles of equal___are congruent.
Two circles are congruent if and only if they have equal radii.
by definition we know,
Congruent circles are circles that are equal in terms of radius, diameter, circumference and surface area.
hence, the required answer is radii
Congruent circles that have congruent central angles have
Recall that two circles are congruent if they have the same radii. Prove that equal chords of congruent circles subtend equal angles at their centres.