Symbolics Help

[ELSID]

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.

[RichardJ]

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

[ELSID]

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?

[RichardJ]

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

[AlanStevens]

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

[RichardJ]

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.

[ELSID]

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 ) .

[AlanStevens · Accepted solution]

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

[ELSID]

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

[Werner_E]

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.

[ELSID]

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!

[Werner_E]

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.