... ollary 3 .11(i), we haveϕ= ψ∞= ψ; a contradiction. 8 The James constant of normalized norms on R2Proof. For our convenience, we write ·instead of ·ψ,ψ∞. Let x, y ∈ Sψ-∞.Weprovethateitherx ... gives the exact value of the James constant of thesespaces.Theorem 3.7. Let ψ∈ Ψ2. ThenJψ-∞=1+1/2ψ(1/2). (3.24)THE JAMES CONSTANT OF NORMALIZED NORMS ON R2WEERAYUTH NILSRAKOO ... Journal of Nonlinearand Convex Analysis 4 (2003), no. 3, 399–410.[10] K S. Saito, M. Kato, and Y. Takahashi, Von Neumann-Jordan constant of absolute normalized norms on C2, Journal of Mathematical...