set a = the strict Subspace of V;

set D = { the strict Subspace of V};

take { the strict Subspace of V} ; :: thesis: for x being set st x in { the strict Subspace of V} holds

x is strict Subspace of V

thus for x being set st x in { the strict Subspace of V} holds

x is strict Subspace of V by TARSKI:def 1; :: thesis: verum

set D = { the strict Subspace of V};

take { the strict Subspace of V} ; :: thesis: for x being set st x in { the strict Subspace of V} holds

x is strict Subspace of V

thus for x being set st x in { the strict Subspace of V} holds

x is strict Subspace of V by TARSKI:def 1; :: thesis: verum