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Plot indefinite integral different than evaluating definite integral?

Posted 6 years ago

Hello,

I've been stuck on this issue for a few hours on with no end in sight. I'm calculating the friction force on a pile at a given depth (let's say 100 feet deep). When I integrate the unit friction (i.e. force per foot of pile), with respect to the pile length, and plot the indefinite integral I get a curve with discontinuities at 5-10 feet and 50 feet. These depth values correspond to piecewise functions I defined for soil layers. They should not show up in the in the integral, though. When I evaluate the same expression using a definite integral from 0 to 100 feet, the value I get is different than what the plot of the indefinite integral shows at 100 feet. The difference between the two is equal to the offset of the curve at the discontinuity shown in the plot. Can anyone shed light on why the indefinite integral is resulting in a curve that matches with the results from a definite integral? The issue can be seen at input line 40.

Thank you in advance for your time.

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POSTED BY: jonathan

It would be helpful to have a self-contained example. That is a lot of examples and difficult to figure out what corresponds to points of issue.

If the code is in Wolfram LanguageInputForm in the post, all the better. I really do not like having to figure out how to resize a windo that was set to full screen and thus blocks all menus.

POSTED BY: Daniel Lichtblau
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