√(q-p)^2 + (p-q)^2
√ [ (q-p)^2 + (p-q)^2 ] simplify......note ...... (q - p)^2 = (p - q) ^2
√([ (p - q)^2 + (p - q)^2] =
√[ 2 (p - q)^2 ] =
(p - q)√2
