Prove that the chords corresponding to congruent arcs of a circle are congruent.

A point on the midpoint of the radius of a circle lies in its:

Name the chord of the circle.

The radii of two circles are 19 cm and 9 cm respectively. Find the radius of the circle which has circumference equal to the sum of the circumferences of the two circles.

Name the diameter of the circle.

The length of the longest chord of a circle of radius $5 \mathrm{cm}$ is

Is $\mathrm{XY}=2 \mathrm{OZ}$?