헤론의 공식(비교)

[math(\displaystyle \begin{aligned} \dfrac{1}{4a^{2}}(a+b+c)(a+c-b)(a+b-c)(b+c-a) \end{aligned})],

[math(\displaystyle \begin{aligned} \dfrac{1}{4a^{2}}\cdot 2s \cdot 2(s-b)\cdot 2(s-c)\cdot 2(s-a) \end{aligned})],

[math(\displaystyle \begin{aligned} \dfrac{4}{a^{2}}s(s-a)(s-b)(s-c) \end{aligned})] 가 되는데,