Angles in a cyclic quadrilateral:

Move points B and D
What do you notice about the sum of [math]\angle[/math]DAB and [math]\angle[/math]DCB?
[b]Angles in a cyclic quadrilateral:[br][/b]Opposite angles in a cyclic quadrilateral add to 180[math]^\circ[/math]
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Information: Angles in a cyclic quadrilateral: