Equal chords are equidistant from the centre of the circle

Sliders for changing the following: 1. Radius of the circle, 2. Length of OX and OY and, Red dots for rotating the respective chords: 1. CD and AB. Pre-requisite knowledge and terms: Pythagoras Theorem, Perpendicular bisector, Radius, Chords, Equidistant Task: Rotate the point X and point Y accordingly for Q1 Q1. Observe that there are two chords, AB and CD. What is the circumstance/situation will the chord CD and AB be equal?