A friend of mine showed this problem he translated from a physics olympiad but I can't solve it:
Consider a perfectly symmetrical compass. It is constituted by two rigorously equal connecting rods, that join in a vertex the one that we call “pivot”. The opening angle is regulable. Imagine that we suspend the compass for the tip of one of the connecting rods, attaching it to a wire whose other end is attached at the ceiling.
a) Sketch the position of the bar at various angles of opening.
b) What is the opening angle of the compass, so that the pivot is the highest possible?
Hint: The center of mass of the bar, assuming that the rods have densities
uniform is the point where the bisector of the angle of the bar crosses the line
passing through the midpoint of both rods. The mass center has to be, for any angle of opening, in the vertical line of the point of suspension of the wire."
Sorry for the english in the translation. My question is how do you solve this geometrically (I know it seems like physics but the problem is all about geometry)