Inputting complicated equation into Wolfram

Question

I am having a bear of a time getting this equation into Wolfram so I can solve it for E(r) = 1000.

Everything is constant except for little r, which is the cursive r in each term. In case anyone is wondering, this is the expression for the electric field from the center of a hydrogen atom. r is for radius.

Can anyone put this in and link me to the solution? Much appreciated.

Answer 1

Here is one approach, but you can put in your constants and then play around with defining them using the proper names.

  solve (.2)/(4 pi .5 r^2)(1 - e^(-2 r /.6)(2(r/.6)^2+2(r/.6)+1)) = 1000 for r

See this WA page.

By defining parameters, I mean, something like:

 q = .2, solve (q)/(4 pi .5 r^2)(1 - e^(-2 r /.6)(2(r/.6)^2+2(r/.6)+1)) = 1000 for r

Here you can define your parameters:

q=.2, t = .4, a=.6, solve (q)/(4 pi t r^2)(1 - e^(-2 r /a)(2(r/a)^2+2(r/a)+1)) = 1000 

For the parameters you posted, I got two solutions:

• $\large r = 7.71723 \times 10^{-20}$
• $\large r = 1.19945 \times 10^{-6}$

Note, there are other options:

• Get a free CAS like SAGE, Maxima or others. These also have working online copies.
• Use Mathics.org