Binomial Theorem:

{(a + b)}^{2} = a^{2} + b^{2} + 2 a b

E = (\begin{matrix} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{matrix})

c = \sqrt{a^{2} + b^{2}}