The Sum of Measures of the Accumulative Angles at a Point

Definition

In the opposite figure, AB, AC, AD, and AE are rays start at A. The angles BAC, CAD, DAE, and EAB are called accumulative angles at the point A.









Theorem

The sum of accumulative angles at a point is 360º.
Please enable Java for an interactive construction (with Cinderella).
Drag free points A, B, C, D, or E to realize that the sum of accumulative angles at a point is 360º.