:: deftheorem defines isometric-like REAL_NS3:def 6 :
for V, W being RealNormSpace
for L being LinearOperator of V,W holds
( L is isometric-like iff ex k1, k2 being Real st
( 0 <= k1 & 0 <= k2 & ( for x being Element of V holds
( ||.(L . x).|| <= k1 * ||.x.|| & ||.x.|| <= k2 * ||.(L . x).|| ) ) ) );