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May 15, 2011
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Interesting Integrations

  • May 15, 2011
  • 1 reply
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I was using the symbolic processor to calculate a very simple integration.

Header 1Header 2Header 3Header 4Header 5
Integraten.A.cos(n.x)n.B.sin(n.x)E.cos(n.x)F.sin(n.x)
MathCad-Definite integralA.sin(x.n)2.B.sin((x.n/2)^2)(E.sin(x.n))/n2.F.sin((x.n/2)^2)
Hand/CalculationA.sin(x.n)-B.cos(x.n)E.sin(n.x)/n-F.cos(n.x)/n
Mathcad-Indefinite integralA.sin(x.n)-B.cos(x.n)E.sin(n.x)/n-F.cos(n.x)/n

Is it possible to use definite integration only for case where there will be no division by zero. It is easy in this example to do it myself however if the calculation is a bit complicated (and done symblically). Is there a way to tell MathCad use definite integration as long as there is no division by zero.

Example

Integrate.bmp

Best answer by AlanStevens

Chad G. wrote:

I was using the symbolic processor to calculate a very simple integration.

Header 1Header 2Header 3Header 4Header 5
Integraten.A.cos(n.x)n.B.sin(n.x)E.cos(n.x)F.sin(n.x)
MathCad-Definite integralA.sin(x.n)2.B.sin((x.n/2)^2)(E.sin(x.n))/n2.F.sin((x.n/2)^2)
Hand/CalculationA.sin(x.n)-B.cos(x.n)E.sin(n.x)/n-F.cos(n.x)/n
Mathcad-Indefinite integralA.sin(x.n)-B.cos(x.n)E.sin(n.x)/n-F.cos(n.x)/n

Given that cos(A) = 1-2,sin(A/2)^2, if you are integrating from 0 to x, the definite integral expressions in your table are correct (if a little unexpected!).

Is it possible to use definite integration only for case where there will be no division by zero. It is easy in this example to do it myself however if the calculation is a bit complicated (and done symblically). Is there a way to tell MathCad use definite integration as long as there is no division by zero.

You could use a programmed function to test the value of n and only call the integral (defined earlier as a function) if it is non-zero.

Alan

1 reply

19-Tanzanite
May 15, 2011

Chad G. wrote:

I was using the symbolic processor to calculate a very simple integration.

Header 1Header 2Header 3Header 4Header 5
Integraten.A.cos(n.x)n.B.sin(n.x)E.cos(n.x)F.sin(n.x)
MathCad-Definite integralA.sin(x.n)2.B.sin((x.n/2)^2)(E.sin(x.n))/n2.F.sin((x.n/2)^2)
Hand/CalculationA.sin(x.n)-B.cos(x.n)E.sin(n.x)/n-F.cos(n.x)/n
Mathcad-Indefinite integralA.sin(x.n)-B.cos(x.n)E.sin(n.x)/n-F.cos(n.x)/n

Given that cos(A) = 1-2,sin(A/2)^2, if you are integrating from 0 to x, the definite integral expressions in your table are correct (if a little unexpected!).

Is it possible to use definite integration only for case where there will be no division by zero. It is easy in this example to do it myself however if the calculation is a bit complicated (and done symblically). Is there a way to tell MathCad use definite integration as long as there is no division by zero.

You could use a programmed function to test the value of n and only call the integral (defined earlier as a function) if it is non-zero.

Alan