we are asked to determine the points that when connected form an equilateral triangle inside the circle. Like this:
An equilateral triangle is a triangle that has equal side lengths. When inscribed in a circle the distance between vertices along the circle is the same, therefore, we need to join points in a way that the distance between vertices is equal. We can join point BF, BD, and FD, like this:
Since each point is at the same distance along the circle and therefore, the triangle is equilateral.
