# Documentation question

Asked by Yaakoub El Khamra on 2012-08-17

Please forgive the newbie question but does the equation on the 1st line here:

seem a bit off or do I need to go back and hit the math books?

The full tutorial page: http://fenicsproject.org/featured/2011/pdesys.html

Regards
Yaakoub

## Question information

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Yaakoub El Khamra
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 Mikael Mortensen (mikael-mortensen) said on 2012-08-17: #1

Are you referring to the p grad(v) term? In that case it is there because v grad(p) (from the math books) has been integrated by parts and we have left out the resulting boundary term. (v grad(p) * dx = v * p * n * ds - p * div(v) * dx) Other than that I think its correct except from a few missing dots.

Best regards

Mikael

Den Aug 17, 2012 kl. 2:15 AM skrev Yaakoub El Khamra:

> Question #206052 on CBC.PDESys changed:
>
> Description changed to:
> Please forgive the newbie question but does the equation on the 1st line here:
>
> seem a bit off or do I need to go back and hit the math books?
>
> The full tutorial page:
> http://fenicsproject.org/featured/2011/pdesys.html
>
> Regards
> Yaakoub
>
> --
> contact for CBC.PDESys.

 Yaakoub El Khamra (yelkhamra) said on 2012-08-17: #2

not quite, I was referring to the ":" in the middle of the expression. Is that just a typo?

 Mikael Mortensen (mikael-mortensen) said on 2012-08-17: #3

That's a contraction of two second rank tensors. It's not a typo, google it:-)

Best regards

Mikael

Den 17. aug. 2012 kl. 16:11 skrev Yaakoub El Khamra <email address hidden>:

> Question #206052 on CBC.PDESys changed:
>
>
> Yaakoub El Khamra is still having a problem:
>
> not quite, I was referring to the ":" in the middle of the expression. Is that just a typo?
>
> --