Question

To verify angle sum property of concave and convex pentagon.​

Answer 1

As with any simple polygon, the sum of the internal angles of a concave polygon is π×(n − 2) radians, equivalently 180×(n − 2) degrees (°), where n is the number of sides. ... A polynomial-time algorithm for finding a decomposition into as few convex polygons as possible is described by Chazelle & Dobkin (1985).