Question 56
Show that in a non-equilateral triangle, the following are equivalent:
(a) the angles of the triangle are in arithmetic progression;
(b) the common tangent to the nine-point circle and the in-circle is parallel to the Euler line.
(a) the angles of the triangle are in arithmetic progression;
(b) the common tangent to the nine-point circle and the in-circle is parallel to the Euler line.