Re: [MATHEDCC] Computer Algebra Systems

Jerry Thornhill (jerry_thornhill@sw.cc.va.us)
Sat, 07 Mar 1998 15:38:54 -0500

>I don't know myself, but here's some more data.
>
>The lower bound of zero
>really seems to make a difference. On [0.1,1] the result is immediate.
>
>There is an nInt (numeric integration) function on the 92 which works
>fine on [0,1].
>
>Only the call to the symbolic integration funciton seems problematic.
>According to the TI manual, if there is an antiderivative, That is found
>and used. And the exactness of the answers on anything but a lower bound
>of zero seems to confirm that. But obviously zero gums up the works.
>

And still more data. It doesn't matter that zero is the lower bound. It
causes problems as well as an upper bound. But it is clearly zero as a
_limit_ that causes the trouble. The interval [-1,1] is nearly
instantaneous. Pressing diamond enter to force an approximation on [0,1]
is very fast. Setting the calculator to approximate mode generates quick
answers. Of course, there is an antiderivative and I've told my students
to just find it, store it in f(x), and use the Fundamental Theorem to
evaluate the integral in cases like this. It takes about 10 seconds to do
that.

I'm glad to have company in trying to figure this out.

Jerry

Jerry Thornhill
jerry_thornhill@sw.cc.va.us
Southwest Virginia Community College
PO Box SVCC
Richlands, VA 24641-1510
540 964 7328

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