Lengthy symbolic equations

[ptc-3082077]

I have to evaluate two fairly messy equations,

in terms of several radii and pressures, which I only know symbolically. I have solved these by hand and, as expected, get my sigmas in terms of the radii and pressures. But the expressions are lengthy and I need to use them in other equations. Is there a way I can write expressions which maintain the symbolic placeholders for my varibles?

[ptc-3082077]

I tried to post the equations in the body of the first post, but here are the expressions I am using.

[Werner_E]

Stuart Daniel wrote:

I have to evaluate two fairly messy equations,

in terms of several radii and pressures, which I only know symbolically. I have solved these by hand and, as expected, get my sigmas in terms of the radii and pressures.

Why didn't you let Mathcad do the work?

But the expressions are lengthy and I need to use them in other equations. Is there a way I can write expressions which maintain the symbolic placeholders for my varibles?

Not sure but I think what you need is to make them functions of all variables. See if the attached would help.

[ptc-3082077]

This was extremely helpful, thank you for the thorough response. Now I am wondering how I may be able to assign arbitrary variables into my functions (i.e. ri=R_0, 1.25R_0...)

[Werner_E]

Stuart Daniel wrote:

This was extremely helpful, thank you for the thorough response. Now I am wondering how I may be able to assign arbitrary variables into my functions (i.e. ri=R_0, 1.25R_0...)

Not really sure what the problem is.

Just define R_0:=2ohm and use it as parameter when calling sigmar(R_0,...)=

What results are you after?

[ptc-3082077]

I am solving this entire problem symbolically. I know my radii only in terms of r_0. I am seeking the pressures P_1 and P_2, which will be in terms of P_0 (which I also only know symbolically).That is why I am wondering if there is a way to go from:

sigma_r(r, r1, r2, p1, p2)

to:

sigma_r(r, 1.25*r_0, 1.5*r_0, p1, p2).

[Werner_E]

Stuart Daniel wrote:

I am solving this entire problem symbolically. I know my radii only in terms of r_0. I am seeking the pressures P_1 and P_2, which will be in terms of P_0 (which I also only know symbolically).That is why I am wondering if there is a way to go from:

sigma_r(r, r1, r2, p1, p2)

to:

sigma_r(r, 1.25*r_0, 1.5*r_0, p1, p2).

You never posted a sheet showing anything of that.

Im not sure if you need a function or wish to solve equations, though.

The attached will at least do what you stated in the last lines - hope it helps.