My Math Forum Sine/Cosine Integral values

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 February 28th, 2008, 02:00 PM #1 Member   Joined: Jan 2008 Posts: 34 Thanks: 0 Sine/Cosine Integral values I don't know how to use cosine integrals or sine integrals - but I had this problem: [-((p*i)/2))Ci(p/2)] + [(p/2)Si(p/2)] + [((p*i)/2)Ci(-p/2)] + (p/2)Si(-p/2)]= ? Where p=pi, i=the imaginary unit, Ci=Cosine integral, Si=Sine integral Can anyone provide an answer to the above value?
 February 28th, 2008, 06:11 PM #2 Member   Joined: Feb 2008 Posts: 89 Thanks: 0 Greetings: The equation simplifies to zero. Note that cos(pi/2) = cos(-pi/2) = 0. Thus we are left with (p/2)Si(p/2) + (p/2)Si(-p/2) = pi/2 - pi/2 = 0. Regards, Rich B. rmath4u2@aol.com
 February 28th, 2008, 08:32 PM #3 Member   Joined: Jan 2008 Posts: 34 Thanks: 0 No, I don't mean cos(pi/2) or cos(-pi/2) - I know what that is. What I'm trying to do is a cosineintegral/sineintegral. But I don't know how to use them or evaluate them. Can anyone elaborate on how to find the cosineintegral of (pi/2) and (-pi/2) and the sineintegral of (pi/2) and (-pi/2)?
 February 29th, 2008, 09:16 AM #4 Senior Member   Joined: May 2007 Posts: 402 Thanks: 0 Well, it's true that Si(-x)=-Si(x). This cancels the sinintegral. The Ci(-x) for x>0 is, however, not defined. Still, Mathematica gives the value of -pi^2/2.

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