Mistake in integration formula

[PhilipMoore]

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.

[RichardJ · Accepted solution]

Yup, it's a bug.

[PhilipMoore]

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

[RichardJ]

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.

[PhilipMoore]

As a teacher, I like to do things for myself to keep up the old skills.

[AlanStevens]

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

Alan

[PhilipMoore]

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.

[Guest2]

Same Bug in Prime 2.0

[VladimirN]

The result in Mathcad Prime 2.0:

[mzeftel]

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

Mona

[PhilipMoore]

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.

[VladimirN]

I hope for both.