11Για ψ(+∞ ) = ψ (0) = 0 και ψ ∗(x) = ψ(x) έχουμε i⟨p⟩∕ℏ = ∫ +∞ ψ(x)(d∕dx)ψ(x)dx 0 = ∫+∞ − 0 (d∕dx)ψ(x)ψ (x )dx = 0 .