Sides AH and CD of regular octagon ABCDEFGH are extended to meet at point P. What is the degree measure of angle P ?
Each exterior angle will form a 45° angle ...so, in concave quadrilateral CPAB, angles PAB and PCB = 45°.... and angle CBA will form the concave side of the quadrilateral whose measure is 360 - 135 = 225°
So...angle CPA = 360 - 90 - 225 = 45°
+100 
