Gogeometry Problem 179

 dans Euclide Geometry Problem par Harvey Littleman

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From Gogeometry

Using :

• central and inscribed angle

 

• CDEF Rombus =>DC=DE
• ABCD square =>DC=DA
• DA=DC=DE => A, C and E are on the circle with center D and radius AD
• With the theorem of inscribed angle, « the central angle of a circle is twice any inscribed angle” : <ADC=2<CEA
• <ACD=90° => <CEA=45°

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