for n being Element of NAT
for f being PartFunc of REAL,(REAL n) holds
( f is Lipschitzian iff ex r being Real st
( 0 < r & ( for x1, x2 being Real st x1 in dom f & x2 in dom f holds
|.((f /. x1) - (f /. x2)).| <= r * |.(x1 - x2).| ) ) )