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I try to use wolfram Alpa to compute a complex integral,

integrate( 0.0016*v^(-0.5)*(1-exp(-  0.0112*v^0.5))+ 0.0036*v^(-0.5)*(1-exp(-0.0090*v^0.5)))

I get the following result

0.285714 e^(-0.0112 sqrt(v))+0.8 e^(-0.009 sqrt(v))+0.0104 sqrt(v)+constant

I am wondering what this constant means? The reason I am asking is because I need to evaluate the result at certain points of v to obtain a definite integral.

Cheers

agentp
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George
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  • Are you familiar with how integration works? The constant term appears in an indefinite integral since the derivative (taking the reverse process) of the constant term would give zero. If you are integrating between two ordinate values, they should cancel (it would be the same constant term in each case, one subtracted from the other). If you want to evaluate at one point, you're stuck with the constant term unless you have at least one know real data point to calculate what it is. – lurker Oct 28 '14 at 16:30
  • Thanks, I understand, the thing is I am evaluating at two points that are +infinity and 1, I think the constant should cancel, am I right? – George Oct 28 '14 at 16:43
  • Correct. You're going to subtract the eval of the integral at `1` from the eval at infinity. The constant will then cancel. – lurker Oct 28 '14 at 17:02

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