The Sum of Interior Angles of a Polygon
Move Points around to come up with a right triangle.
What degree should the 3 angles be?
No matter where you move your points, what is the AREA?
Plot a midpoint
What is the midpoint?
Now knowing you're midpoint, see how many triangles can be made from midpoint F to points A, B, C, D, and E
How many Triangles are made?
Add angles to the BCF triangle
What are the angles to the BCF triangle?