Peculiar behavior of Integrate
- To: mathgroup at smc.vnet.net
- Subject: [mg2617] Peculiar behavior of Integrate
- From: bruck at mtha.usc.edu (Ronald Bruck)
- Date: Thu, 30 Nov 1995 20:58:17 -0500
Can anyone explain this to me? This comes from Problem G.1.b.iii of problem
set 2.03 of Davis, Porta and Uhl's Calculus and Mathematica:
If I execute
Clear[t,T]
100 + Integrate[(160 E^t)/(0.5 + E^t)^2,{t,0,T}]
%/.T->2400
Mathematica does it in a wink. If I execute
Clear[t,T]
100 + Integrate[(160 E^t)/(1/2 + E^t)^2,{t,0,2400}]
Mathematica does it quick as a wink. (This is on a Power Mac 9500/132;
your winks may vary.)
But if I execute
Clear[t,T]
100 + Integrate[(160 E^t)/(0.5 + E^t)^2,{t,0,2400}]
then Mathematica grinds away... and grinds away... and so far I haven't had
the patience to outwait it. When I interrupt the kernel it takes almost a
minute to back out of whatever it's doing.
What's it doing? Is this some local user-preference which is causing this?
Can anyone verify similar behavior on other platforms?
This is Mathematica 2.2.2.1 for the Power Macintosh (the printing-magnifi-
cation-but-fix version).
I asked the student whether she had made the proper propitiary sacrifices
before sitting down at the computer, and she swore she had ;-)
--Ron Bruck