Talk:Brahmagupta's formula

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Brahmagupta's method

How did Brahmagupta derive this formula? The algebra and trigonometry in the modern proof surely post-date him by a considerable amount. Rigadoun 04:58, 12 May 2006 (UTC)[reply]

He didn't have the trig formula--see below. Duoduoduo (talk) 16:38, 13 June 2012 (UTC)[reply]

Generalized formula is not Brahmagupta's

Ever since the edit of 12:22, 16 May 2004 by Rjyanco, the lede has said (with slight tweaks to the wording):

In Euclidean geometry, Brahmagupta's formula finds the area of any quadrilateral given the lengths of the sides and some of the angles. In its most common form, it yields the area of quadrilaterals that can be inscribed in a circle.

This is not right--Brahmagupta's formula is the special case formula applying only to the cyclic case. See for example the Mathworld article . I'm changing the lede to reflect this. Duoduoduo (talk) 16:38, 13 June 2012 (UTC)[reply]