△GCE, from the external angle theorem, we get ∠1= ∠ c+∠ e.
Similarly, ∠ 2 = ∠ B+∠ D.
△AGH, which is derived from the theorem of sum of internal angles.
∠A+∠ 1+∠2= 180?
∴∠A+∠B+∠C+∠D+∠E= 180?
The sum of the five angles of the five-pointed star is 180 degrees.