Talk:Bretschneider's formula

The diagram shows a cyclic quadrilateral, but cyclic is not relevant? Charles Matthews 09:34, 9 October 2006 (UTC)[reply]

Indeed. Being a cyclic quadrilateral changes the the properties of A and C such that cos2(A+C/2) is simplified ruining the formula. The diagram should be removed or changed to prevent confusion. Merosonox 04:16, 1 November 2006 (UTC)[reply]

Maybe I'm just stupid today, but isn't it the case that the sides labeled on the diagram don't match up with the proof? Shouldn't the first line be something like (1/2)ps sin A + (1/2)qr sin C instead? (Of course, it might be easier to change the diagram than the whole proof, but I haven't time to do either right now...) Babcockd (talk) 14:25, 26 November 2007 (UTC)[reply]

Since I don't know how to fix the diagram, I've changed the proof. Algebraist 19:38, 30 April 2008 (UTC)[reply]