According to the Journal of Irreproducible Results, any obtuse angle is a right angle! Here is their argument. Given the obtuse angle a, we make a quadrilateral ABCD with LDAB = x, and ZABC = 90, and AD = BC. Say the perpendicular bisector to DC meets the perpendicular bisector to AB at P. Then PA PB and PC = PD. So the triangles PAD and PBC have equal sides and are congruent. Thus LPAD = LPBC. But PAB is isosceles, hence LPAB = ZPBA. Subtracting gives x=LPAD - PAB = LPBC - LPBA = 90. This is a preposterous conclusion just where is the mistake in the "proof" and why does the argument break down there?