Talk:Cyclic quadrilateral

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I was wondering - does anyone have a proof for the first and/or fifth item(s) in the list? Aleph2.0 01:19, 22 May 2006 (UTC)

The first external link proves the first item on the list. Lemmy Kilmister 16:35, 13 June 2006 (UTC)

Question: If one the sides of cyclic quadrilateral is equal to radius, is the qudrilateral a square. Explain with proof please. —The preceding unsigned comment was added by 192.88.212.44 (talk • contribs) .

Do concave or crossed quadrilaterals whose vertices lay on a circle count as cyclic quadrilaterals? For example, des Brahmagupta's formula apply to them to? Maybe it is worth mention wether or not this is the case in the article. 130.89.167.52 18:33, 19 October 2006 (UTC)