To explain this question, I would first draw a digram of a circle. Then I woud add a chord and create triangles with vrtices at the circumference of the circle which all have the chord as a base. Next, I would point out the angles which are equal and make a point that they have to touch circumference of the circle on all three sides, be subtended by the same chord and be in the same segment of the circle. I would also draw the diagram in the form of a "bow-tie" because that is a very common way to test knowledge of the theorem at GCSE, which students often misunderstand. Using that diagram I would again point out the angles which are equal, highlighting the chords that subtend them. If possible I would use different colours for the different angles.