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Bill Simpson
05/01/12 12:05pm

Since your Piecewise function appears to only be a unit step function, pull that step out into the bounds of integration. This then appears to integrate almost instantly.

In[1]:= f[x_]:=Sin[x];q=1/E;
Integrate[Integrate[x f'''[x],{x,0,Min[1/q,1+u-Floor[q]]}, Assumptions->q>0],{u,0,1/q}, Assumptions->q>0]

Out[3]= E-Cos[1]-Cos[E]+E Cos[E]+2 Sin[1]-2 Sin[E]-E Sin[E]

Be careful that you get the bounds of integration correct. If you can see how to get rid of that Min[] it would probably be even better.

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Subject (listing for 'symbolic integral calculates infinitly long')
Author Date Posted
symbolic integral calculates infinitly long igor_igel 04/27/12 8:29pm
Re: symbolic integral calculates infinitly long Bill Simpson 05/01/12 12:05pm
Re: Re: symbolic integral calculates infinitly ... Peter Pein 05/02/12 03:09am
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