0 5 10 15 20 0 0.0 0.2 0.4 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 Ya(x) x ◊ ◊ ◊ ◊ ◊ ◊ Y0(x) Y1(x) Y2(x) Y-1(x) Y-2(x) Y0 zero Y1 zero Y2 zero Y-1 zero Y-2 zero Zeros of Neumann Ya(x)