5. Construction of the circumcircle (red) and the circumcenter Q (red dot). This construction clearly shows how to draw the angle bisector of a given angle with compass and straightedge or ruler. 2. 2. Example Definitions Formulaes. This page shows how to construct (draw) the circumcenter of a triangle with compass and straightedge or ruler. The construction first establishes the circumcenter and then draws the circle. 1. Assume that there is just one centre that is the centre C. Again we take a rule and a compass. • as a centre B draw an arc of radius 2.5cm which intersects at point C iv). Steps for construction: I) Construction of triangle. Step:2 Place the compass point on the circumcenter O and stretch to any one of the vertices of the given triangle. Construct the circumcircle of the triangle ABC with AB = 5 cm,