; This is how we arrive at Heron's formula for the area
; of any triangle, given side lengths a, b, and c.
; Brahmagupta's formula for the area of a cyclic quadrilateral is used,
; making one side length equal zero, to make a cyclic triangle.
; Since all triangles are cyclic (can be circumscribed by a circle),
; this gives the area for any triangle.

2s=a+b+c+d ; cyclic quadrilateral side lengths are a, b, c, and d
area = ((s-a)*(s-b)*(s-c)*(s-d))^.5
eliminate s ; Brahmagupta's formula:
copy
replace d with 0 ; Heron's formula: