theorem Th84: :: TOPREAL6:91

for r1, r2, s1, s2 being Real
for u, v being Point of (Euclid 2) st u = |[r1,s1]| & v = |[r2,s2]| holds
dist (u,v) = sqrt (((r1 - r2) ^2) + ((s1 - s2) ^2))