topic Re: Symbolics Help in Mathcad

Symbolics Help

ELSID — Thu, 03 May 2018 17:49:36 GMT

Working with symbolics is not my strong point. Need a little help with questions on the sheet. Based off of Dr. Alan Stevens critical thickness insulation work. Mostly symantics ... so driving me crazy.

Re: Symbolics Help

RichardJ — Thu, 04 Oct 2012 20:39:22 GMT

One thing you should always remember when using the symbolic processor is that it does not make implicit assumptions like you do. If it doesn't do what you expect then a liberal dose of the "assume" keyword can work wonders

Re: Symbolics Help

ELSID — Thu, 04 Oct 2012 21:12:18 GMT

Arrg! I had the R and t>0 on a previous section ... thanks for the catch. Is there a way of forcing the 2pi to the numerator? What about the negative sign?

Re: Symbolics Help

RichardJ — Thu, 04 Oct 2012 21:22:00 GMT

Solve first, then simplify to get rid of the weird formatting, then force the ln formatting.

Re: Symbolics Help

AlanStevens — Thu, 04 Oct 2012 21:33:14 GMT

ElSid wrote:
Is there a way of forcing the 2pi to the numerator?

Think of P/2pi as P1 and solve for P1. Then set P:=P1*2pi ->

What about the negative sign?

Replace T.sat with either T.s or just Tsat (i.e. no subscript) It will then result in T.s - T.air rather than -(T.air - T.sat ) .

Alan

Re: Symbolics Help

RichardJ — Thu, 04 Oct 2012 21:51:00 GMT

Replace T.sat with either T.s or just Tsat (i.e. no subscript) It will then result in T.s - T.air rather than -(T.air - T.sat ) .

Interesting observation. I wonder why that makes any difference. I would expect the formatting to be independent of the choice of variable name.

Re: Symbolics Help

ELSID — Thu, 04 Oct 2012 22:18:29 GMT

Did not understand the second part

AlanStevens wrote:
--> Replace T.sat with either T.s or just Tsat (i.e. no subscript) It will then result in T.s - T.air rather than -(T.air - T.sat ) .

Re: Symbolics Help

AlanStevens — Fri, 05 Oct 2012 07:44:11 GMT

ElSid wrote:
Did not understand the second part
AlanStevens wrote:
--> Replace T.sat with either T.s or just Tsat (i.e. no subscript) It will then result in T.s - T.air rather than -(T.air - T.sat ) .

See attached.

Alan

Re: Symbolics Help

ELSID — Thu, 18 Sep 2014 19:35:54 GMT

Revisitng a post with a file that I had working in MathCAD 14 and for some reason will not work in MathCAD 15 M030. Hoping the Collab can help. Problem starts with equation 5 where it appears I can not longer define a variable based on a symbolic. See screenshot

Re: Symbolics Help

Werner_E — Thu, 18 Sep 2014 20:23:25 GMT

Thats "normal" (nevertheless strange) behaviour that you dont see a symbolic result when you use a symbolic inline evaluation in an assignment.

Simply evaluate P.F later and you will see the correct result.

You used a font which seems not to be installed on my machine, so the nominator is shown as a small rectangle.

Depending on how wide you'd like your sheet to be spread you might consider changing that.

Re: Symbolics Help

ELSID — Thu, 18 Sep 2014 20:30:07 GMT

Werner,

MathCAD just crashed. Why did it work in MathCAD 14? You are correct and I will revise the sheet. I shouldn't have to to do this much re-work btween 14 and 15!

Re: Symbolics Help

Werner_E — Fri, 19 Sep 2014 10:31:09 GMT

ELSID wrote:
Werner,
MathCAD just crashed. Why did it work in MathCAD 14? You are correct and I will revise the sheet. I shouldn't have to to do this much re-work btween 14 and 15!

I am using MC15 (M030) and didn't experience that kind of problem.