In geometry, proving two angles are equal often involves understanding the properties of circles. When considering a circle with diameter OC, the angles subtended by the endpoints of the diameter at any point on the circle are right angles. This means that if two angles are formed by lines intersecting at points on the circumference, and one of those lines is a diameter, the angles are equal. Utilizing the inscribed angle theorem can also aid in establishing angle equality. Understanding these principles is crucial for solving related geometric problems effectively.