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## How to tell MathCAD something is constant  1-Newbie

## How to tell MathCAD something is constant

In the highlighted integration, I want to tell MathCAD that the c is constant, but have not been able to figure out how to do so. I've seached some, but no luck.

Thanks

1 ACCEPTED SOLUTION

Accepted Solutions  24-Ruby IV
(To:ptc-4168940)

No need to tell Mathcad so, Mathcad's symbolic treats c as a constant (for MC's numeric c is velocity of light)

I guess you are puzzled as of the huge expression you get in evaluating that integral while you would have expected something like But while Mathcad treats c as a constant it has to consider all possibilities, c could be -v1, it could be complex, etc.

So Mathcad gives you the results with a lot of if's to cope for every eventuality.

Your function has a vertical asymptote at v=-c, so the bounderies of your definite integral have to be both at the left or both at the right of -c, otherwise the integral would have to be infinity. Obviously c must not be -v1 or -v2 or you would get a divison by zero.

Replace c by a number and see that Mahcad still has some ifs, but less as with an unknown c.

You might try to use assume to get a more meaningful result. Unfortunately "assume" very often does not work as expected. E.g. "assume, -c<v1<v2" should do the job, but doesn't.

EDIT: Interestingly enough "assume, -c < v1" does the job - thats crazy! In fact "simplify" would not be necessary here, typing it is just a reflex 😉

5 REPLIES 5  24-Ruby II
(To:ptc-4168940)

c:=c

and than the integral

PS

May be this will be interesting for you

http://twt.mpei.ac.ru/TTHB/2/tdceng.html   1-Newbie
(To:ValeryOchkov)

That is an awesome site. Inspires me to go learn a little Russian.  24-Ruby II
(To:ptc-4168940)
 Samuel Bernstel wrote:That is an awesome site. Inspires me to go learn a little Russian.

Thanks!

I try to translate the site into English but...

Can You help me? Point me please pages of the site and I will translate its.

Some my article in English in this area (themogynamic + Mathcad) You can see here http://twt.mpei.ac.ru/ochkov/work2_eng.htm  24-Ruby IV
(To:ptc-4168940)

No need to tell Mathcad so, Mathcad's symbolic treats c as a constant (for MC's numeric c is velocity of light)

I guess you are puzzled as of the huge expression you get in evaluating that integral while you would have expected something like But while Mathcad treats c as a constant it has to consider all possibilities, c could be -v1, it could be complex, etc.

So Mathcad gives you the results with a lot of if's to cope for every eventuality.

Your function has a vertical asymptote at v=-c, so the bounderies of your definite integral have to be both at the left or both at the right of -c, otherwise the integral would have to be infinity. Obviously c must not be -v1 or -v2 or you would get a divison by zero.

Replace c by a number and see that Mahcad still has some ifs, but less as with an unknown c.

You might try to use assume to get a more meaningful result. Unfortunately "assume" very often does not work as expected. E.g. "assume, -c<v1<v2" should do the job, but doesn't.

EDIT: Interestingly enough "assume, -c < v1" does the job - thats crazy! In fact "simplify" would not be necessary here, typing it is just a reflex 😉  24-Ruby II
(To:Werner_E)
 Werner Exinger wrote:No need to tell Mathcad so, Mathcad's symbolic treats c as a constant (for MC's numeric c is velocity of light)  Announcements
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