1. Place your compass point on A and measure the distance to point B. Swing an arc of this size above (or below) the segment. 2. Without changing the span on the compass, place the compass point on B and swing the same arc, intersecting with the first arc. 3. Label the point of intersection as the third vertex of the equilateral triangle.
In order to construct an equilateral triangle, within a circle you will need a compass, a straight edge, and a right angle drafting triangle, any flat object with a true 90 degree angle, can be used.
