Heron's formula

== English == === Alternative forms === Hero's formula === Etymology === Named after Hero of Alexandria. === Proper noun === Heron's formula The formula A = s ( s − a ) ( s − b ) ( s − c ) {\displaystyle A={\sqrt {s(s-a)(s-b)(s-c)}}} , where a, b, and c are the sidelengths of a triangle, s is its semiperimeter, and A is its area.