Given angle(PQR) begin as you would when bisecting the angle: http://www.mathopenref.com/constbisectangle.html http://www.mathopenref.com/constbisectangle.html.

Given angle(PQR) begin as you would when bisecting the angle: http://www.mathopenref.com/constbisectangle.html http://www.mathopenref.com/constbisectangle.html. Your arc intersections with |PQ| and |RQ| (call them p & q) give you an isosceles triangle pQr. Construct an equilateral triangle on |pr| similar to: http://www.mathopenref.com/constequilateral.html http://www.mathopenref.com/constequilateral.html