Triangle knowing the vertex A, the line r joining A and B and the ninecircle c

1) Draw the perpendiculars s and t to the r from the points where r cuts c.
2) Draw the circle with center A and radius twice the radius of c.
3) This circle cuts s at a point X.
4) Draw the circle with center X and radius twice the radius of c.
5) This circle cuts r at B and t at C, and ABC is the requested triangle.