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Mathematical gce
Solution: As shown in the figure.

△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.