We may analyze ''X''<sup>2</sup> = {‹''u'', ''v''› : ''u'', ''v'' ∈ ''X''} into two parts, specifically, the pairs that lie on and off the diagonal: | We may analyze ''X''<sup>2</sup> = {‹''u'', ''v''› : ''u'', ''v'' ∈ ''X''} into two parts, specifically, the pairs that lie on and off the diagonal: |