Abstract.A geometric approach to the improvement of Blundon's inequalites given in [11] is presented. If φ = min{|A − B|,|B −C|,|C − A|}, then we proved the inequality − cos φ cos ION cos φ , where O is the circumcenter, I is the incenter, and N is the Nagel point of triangle ABC . As a direct consequence, we obtain a sharp version to Gerretsen's inequalities [7].Mathematics subject classification (2010): 26D05, 26D15, 51N35.