Question 955644
An arc is directly related to the measure of the central angle; and your intersecting diameters are perpendicular at their intersection point, center of the circle.


Can you see a plan of steps using reasons:
Vertical angles are congruent;
Perpendicular segments mean Right Angles;
Congruent central angle of circle subtend congruent arc measures.


Not a full proof, but just a raw outline of how to justify what statements you could say.