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PhilipMoore1-Visitor
1-Visitor
March 8, 2012
Solved

Mistake in integration formula

  • March 8, 2012
  • 5 replies
  • 4778 views

A student asked mathcad to supply an antiderivative. Not quite believing the answer, she factored the integrand and tried again and recieved a different (this time correct) answer.

I've attached the file which shows the incorrect antiderivative and a line in which I differentiate the incorrect antiderivative and do not arrive at the original function.

Best answer by RichardJ

Yup, it's a bug.

5 replies

R
RichardJ19-TanzaniteAnswer
19-Tanzanite
March 8, 2012

Yup, it's a bug.

P
PhilipMoore1-VisitorAuthor
1-Visitor
March 8, 2012

If you haven't already checked by hand, the denominator should be a 6, not a 3.

R
RichardJ19-Tanzanite
19-Tanzanite
March 9, 2012

Hand? No, I checked using the old Maple engine in Mathcad 13. With a reliable symbolic processor one doesn't need to check it by hand.

A
AlanStevens19-Tanzanite
19-Tanzanite
March 9, 2012

Strangely, just changing the denominator to (6-y)y produces the right answer!

Alan

P
PhilipMoore1-VisitorAuthor
1-Visitor
March 9, 2012

My guess is that a programmer incorrectly typed in the formula for int( 1/ ( variable^2 - a * variable) dvariable) and that incorrect formula is being used.

Yet, if you factor it, it prompts the program to try integration by parts.

Mathcad does do the partial fractions on the fraction if you ask it to.

G
Guest21-Visitor
1-Visitor
March 9, 2012

Same Bug in Prime 2.0

V
VladimirN24-Ruby III
24-Ruby III
March 12, 2012

The result in Mathcad Prime 2.0:

Pic_1.png

M
mzeftel1-Visitor
1-Visitor
March 12, 2012

I logged the bug to be fixed in the next release.

Mona

P
PhilipMoore1-VisitorAuthor
1-Visitor
March 12, 2012

To be clear, is that the next release of MathCad prime, Mathcad, or both?

I've been chatting with the chair for our math department, wondering if Mathcad is still being updated now that Mathcad Prime is released.

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