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## Symbolics Help

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.

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Accepted Solutions

## Re: Symbolics Help

 `ElSid wrote:Did not understand the second partAlanStevens 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

11 REPLIES 11

## Re: Symbolics Help

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

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

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

## Re: Symbolics Help

 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

 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

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

 `ElSid wrote:Did not understand the second partAlanStevens 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

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

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.

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