Skip to main content
Z
ZeusEscudero1-Visitor
1-Visitor
July 1, 2013
Solved

Integration Error

  • July 1, 2013
  • 2 replies
  • 3415 views

Dear Community:

I am user of MathCad 15. Integrate operation does not work. Integrate( t + a )dt answers 1/2( t + a )^2 instead of 1/2 t^2 + a t.

Shoud I install again MathCad?

Is it a known bug?

Where can I download patches?

Zeus.

Best answer by ZeusEscudero

Thank you for your help.

I found that, to make the initial conditions equal 0 or the additive constant equal 0, I must use definite integral from 0 to t in this case.

Definite_Integral.png

Which is the result, in a simple way, that I was looking for.

Thank you again.

Zeus

2 replies

A
AlanStevens19-Tanzanite
19-Tanzanite
July 1, 2013

Zeus Escudero wrote:

... Integrate( t + a )dt answers 1/2( t + a )^2 instead of 1/2 t^2 + a t.

...

1. What do you think you would get if you differentiated 1/2( t + a )^2 wrt t?

2. Indefinite integration is only defined up to an arbitrary constant (which Mathcad sets to zero).

3. Expand 1/2( t + a )^2? and compare with 1/2 t^2 + a t, bearing in mind comment number 2.

Alan

Z
ZeusEscudero1-VisitorAuthor
1-Visitor
July 1, 2013

Dear Alan:

The definite integral from 0 to t works ok. Are there options or preferences to force making the integration constant equals to 0? (as viewed 1/2 a^2 as inategration constant is so arbitrary).

Thanks

Zeus

A
AlanStevens19-Tanzanite
19-Tanzanite
July 1, 2013

You could do the following:

Integ.PNG

Alan

Z
ZeusEscudero1-VisitorAuthorAnswer
1-Visitor
July 1, 2013

Thank you for your help.

I found that, to make the initial conditions equal 0 or the additive constant equal 0, I must use definite integral from 0 to t in this case.

Definite_Integral.png

Which is the result, in a simple way, that I was looking for.

Thank you again.

Zeus

W
Werner_E25-Diamond I
25-Diamond I
July 2, 2013

Well, fine if it works for the functions you are dealing with.

But keep in mind that this "method" will not get rid of all constants and may even add one.

Sometimes you may even get erranous results.

Furthermore I would suggest not using the same variable for integration and limit.

integrals.png

Terms & ConditionsAccessibility statement