Numerical error

Forum|Forum|15 years ago
January 12, 2011
2 replies
5608 views

Hi all,

I'm using Mathcad 2001i (as part of a Open University course) and have hit a problem. I was wondering if anyone would care to take a look and see if it can be easily resolved. I've attached the doc.

Basically I'm trying to find local maxima and minima of an expression. The expression itself is generated partly numerically but if I copy the expression using manually entered coeff values with the "same" values, I don't experience a problem. I've put the latter case on the second page down in the doc. Hopefully it's not too difficult to fathom.

I know the maxima and minima exist because I can see them on the graph plots (also illustrated).

Regards,

Dave W.

1_remez-mcd.zip

Other

M

MikeArmstrong

1-Visitor

Hi David, welcome to the forum.

What course are you studying at the Open University. I completed the Structural Integrity module from the Engineering degree last year.

Mike

D

DaveWooff

Author

10-Marble

Hi Mike,

thanks for the welcome.

Mathematical Modelling MST209. Actually I've finished (and passed!) now so I'm contemplating my next move. Still badly bruised though. It was quite heavy going.

Thanks,

Dave W.

L

LucMeekes

23-Emerald IV

Hi David,

My Mathcad 11 gives 0.566202034099714 as answer for the first (upper, marked yellow) root.

The second (lower, also marked yellow) root results in 0.566202034099816

With the first difference on the 13th significant digit I think that's sufficiently equal.

What values do you see in Mathcad 2001i?

Luc

D

DaveWooff

Author

10-Marble

Hi Luc,

it's helpful to know that a different version of Mathcad is able to deal with it. I get a convergence error - on the first yellow highlighted derror().

Is it possibly a limitation of an old version of Mathcad do you think?

Ta, Dave.