Solve::ivar: 0 is not a valid variable.

• To: mathgroup at smc.vnet.net
• Subject: [mg129083] Solve::ivar: 0 is not a valid variable.
• From: Ding Yuan <gardener_2003 at hotmail.com>
• Date: Thu, 13 Dec 2012 04:08:50 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Delivered-to: l-mathgroup@wolfram.com
• Delivered-to: mathgroup-newout@smc.vnet.net
• Delivered-to: mathgroup-newsend@smc.vnet.net

```Hello,

I am fresh in Mathematica. Can anyone explain what is happening in this code?

Cheers

Ding

------------
gamma = 1.5; m = 0;
C0 = 1.; CA = 2;
CF = (C0^2 + CA^2)^0.5; CT = (C0 CA)/CF;
Ce = 0.5; CAe = 5 ;
CFe = (Ce^2 + CAe^2)^0.5; CTe = (Ce CAe)/CFe;
delta = (2 C0^2 + gamma CA^2)/(2 Ce^2 + gamma CAe^2);
kza = 1.;
k0[x_] := (-(((x^2 - C0^2) (x^2 - CA^2) )/((C0^2 + CA^2) (x^2 -
CT^2))))^0.5
ke[x_] := (-(((x^2 - Ce^2) (x^2 - CAe^2))/((Ce^2 + CAe^2) (x^2 -
CTe^2))))^0.5
NSolve[(delta (x^2 - CAe^2) k0[x] BesselI[m + 1, k0[x] kza])/
BesselI[m,
k0[x] kza] + ((x^2 - CA^2) ke[x] BesselK[m + 1, ke[x] kza])/
BesselK[m, ke[x] kza] == 0, {x, 0, 10}, Reals]

NSolve::ivar: 0 is not a valid variable. >>
NSolve[(0.0941502 (-25 +
x^2) (-(((-4 + x^2) (-1. + x^2))/(-0.8 + x^2)))^0.5 BesselI[1,
0.447214 (-(((-4 + x^2) (-1. + x^2))/(-0.8 + x^2)))^0.5])/
BesselI[0,
0.447214 (-(((-4 + x^2) (-1. + x^2))/(-0.8 + x^2)))^0.5] + (
0.199007 (-4 +
x^2) (-(((-25 + x^2) (-0.25 + x^2))/(-0.247525 +
x^2)))^0.5 BesselK[1,
0.199007 (-(((-25 + x^2) (-0.25 + x^2))/(-0.247525 +
x^2)))^0.5])/
BesselK[0,
0.199007 (-(((-25 + x^2) (-0.25 + x^2))/(-0.247525 +
x^2)))^0.5] == 0, {x, 0, 10}, Reals]

```

• Prev by Date: Re: Recurrence Equation RSolve, no error shown, no solution?
• Next by Date: Re: Mathematica 9 does not read mathematica 8 ".mx" files
• Previous by thread: Help with visualization
• Next by thread: Re: Solve::ivar: 0 is not a valid variable.