T公理可知，有formula_7和formula_4的不相交邻域formula_9和formula_10，于是formula_11。取formula_12，使得formula_13，则formula_14。记formula_15是formula_2中所有闭包与formula_4不相交的成员，上面已证明formula_18。记formula_19是formula_2中所有闭包与formula_3不相交的成员，则formula_22。记formula_23，formula_24，则formula_25和fo