"Operation cannot be performed with units" for exponential function

#1 Posted: 6/25/2023 2:26:10 PM

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Hi,

I get the "Operation cannot be performed with units" error for a complicated equation involving exponential functions which seem to be the culprit:

Here's the file:

Operation units.sm (17 KiB) downloaded 26 time(s).

Is there a mistake in this equation in SMath ? Here's what it looks like in the original:

#2 Posted: 6/25/2023 3:31:07 PM

sergio

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The main error you made is in obtaining the pulsation from the frequency.
Also in the formulation of X5 there were two or three errors of evaluation of the SIN (or cos) of the pulsation multiplied by a time (attention to the use of parenthesis)
Operation_units.sm (17 KiB) downloaded 32 time(s).

sergio

#3 Posted: 6/25/2023 4:23:53 PM

EngMath

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Thank you very much. The formula for ω_n from the book did look suspicious to me so I tried removing f_n from it but it didn't help so I thought that the main problem lies somewhere else.

#4 Posted: 6/26/2023 6:13:35 AM

Davide Carpi

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Wrote
Thank you very much. The formula for ω_n from the book did look suspicious to me so I tried removing f_n from it but it didn't help so I thought that the main problem lies somewhere else.

That's a strange hybrid; the equations should be the following:

2023-06-26 11_09_35-Angular frequency - Wikipedia - Mozilla Firefox.png

2023-06-26 11_09_44-Angular frequency - Wikipedia - Mozilla Firefox.png

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#5 Posted: 6/26/2023 11:09:04 AM

EngMath

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How can I plot the result as x(t) for t=0 to t=12 s ? From what I remember, plots require x as a variable so I tried with u(x) but I still can't make it work even with all the occurrences of t replaced with x (although I'd rather avoid doing that):

Operation units fixed with plot.sm (16 KiB) downloaded 34 time(s).

#6 Posted: 6/26/2023 11:41:54 AM

Davide Carpi

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You have to manage the variable [x] and the result [f(x)] units

2023-06-26 16_39_37-SMath Solver - [Operation units fixed with plot.sm_].png

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"Operation cannot be performed with units" for exponential function - Messages