MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

DSolve Issues

I am solving the following Differential Equation

Phi''[r]+2*r^(-1)Phi'[r]+0.104479*Phi[r]==0 and Phi[0]==K (some
constant)   ; kinda has a cos/sin solution

2.71828^(-0.323232 \[ImaginaryI] r) ((0.+
     0. \[ImaginaryI]) + (0.+ 0. \[ImaginaryI]) 2.71828^(
    0.646465 \[ImaginaryI] r) + (0.+ 1.54687 \[ImaginaryI]) K - (0.+
      1.54687 \[ImaginaryI]) 2.71828^(0.646465 \[ImaginaryI] r) K)

all divided by r.

My problem is that Mathematica is not treating those "zeros".... as
well zeros. Thus, the solution cannot really be used. In fact, if I
manually reproduce the solution and remove those "zeros", then the
solution is fine.

I have another similar ODE Anyone have any ideas.

Phi''[r]+2*r^(-1)Phi'[r]- 287.31*Phi[r]==0 and Phi[3R]==0(some
constant)  ; kinda has a cosh/sinh solution

As you might have notice I need to match these two solutions and their
derivatives at some point.  The ratio of which gives me what I desire
the value of R.

Yet, Mathematica treats those "zeros" as something else.

  • Prev by Date: Re: diff equation
  • Next by Date: Re: function to check if array is empty
  • Previous by thread: Re: Inverse of symbolic matrix
  • Next by thread: Re: DSolve Issues