Cyclic quadrilateral

Revision as of 18:18, 18 June 2006 by Dschafer (talk | contribs) (wiki-fied, added properties)

Cyclic Quadrilaterals are quadrilaterals that can be inscribed in circles. They occur frequently on math contests and olympiads due to their interesting properties.


In cyclic quadrilateral $ABCD$:

  • $\angle A + \angle C = \angle B + \angle D = {180}^{o}$
  • $\angle ABD = \angle ACD$
  • $\angle BCA = \angle BDA$
  • $\angle BAC = \angle BDA$
  • $\angle CAD = \angle CBD$

Applicable Theorems/Formulae

The following theorems and formulae apply to cyclic quadrilaterals:

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