substituting constant into slope equation

[XcasEngGuy]

I noticed something interesting. I work a lot with integrating differential equations for bending of beams. After finding the equations for the slope and deflection of a beam, I need to calculate those values at a point on the beam. I have attached the .xws file and the pdf I can create from the Latex produced by Xcas. Note that when I substitute in a constant into the slope equation, the left hand side becomes y', which is perfect and I think is a new feature you have created. Note that if I apply the normal() command to the slope equation the left hand side becomes 0. If I "recreate" the slope equation by setting the left hand side equal to the right hand side, the normal() command works as I would like. I can't figure out what the difference is...

Matt

xcas example.zip

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[parisse]

This issue is related to the fact that x has two different meanings in the same expression: it is the symbolic derivation variable in diff(y(x),x) and it is given a value in the substitution x=L/2.
That's the reason why there is a function_diff command, if you replace diff(y(x),x) by function_diff(y)(x), then x will have only one meaning.

[XcasEngGuy]

Thanks, I'll try that.

[XcasEngGuy]

I am still curious about what's shown in eq18 through eq22 in my example. In eq19 I "recreate" the first equation in eq18 by setting the left hand side equal to the right hand side. After that recreation the normal command functions as I like (eq20 and eq22). However, normal(eq18) does not even though eq18 and eq19 appear identical.

Thank you for your help.