UKMT Cayley Olympiad, 2018

Geometry Difficulty 3.0 AMC 10/12 Prove it United Kingdom

Prove that the difference between the sum of the four marked interior angles $A$ , $B$ , $C$ , $D$ and the sum of the four marked exterior angles $E$ , $F$ , $G$ , $H$ of the polygon shown is $360°$ .

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