formula

\[(a^{2}+b^{2}+c^{2}-ab-bc-ca)=\frac{1}{2}{(a-b)^{2}+(b-c)^{2}+(c-a)^{2}}\]

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'Beauty is truth, truth beauty,'-that is all Ye know on earth, and all ye need to know.
John Keats,"Ode on a Grecian Urn"