I recently bought the TI-92 Plus module. In addition to all the new
features, it cleans up some previous things. Earlier this year, I posted
to this list about trying to integrate x^(n+1) on the TI-92 in a context
where n could be any number greater than 1. The calculator refused to do it
though it integrated x^n without hesitation. The new module will do the
integral with no problem.
I also commented (as did others) about simple definite integrals taking an
incredibly long time. For example, the integral of
x^6 - 2x^5 + x^4 + 3x^3 - 4x^2 + x - 5
with limits of 0 and 1 took several minutes to evaluate. Others commented
that the limit of 0 was the culprit. Again, the new module produces
answers very quickly.
The old circular definition problem has also been resolved.
One minor bug remains unfixed. The TI-92 can do one-sided limits. The
syntax is
limit(expression, variable, point, [direction])
where expression, variable, and point are self-explanatory. I. e.,
limit(x^2,x,3) calculates the limit of the expression x^2 as x approaches
3. This is the standard two-sided limit. The last argument (direction) is
optional. To compute a right hand limit, just enter any positive number.
Thus, limit(x^2,x,3,1) calculates the limit from the right. Similarly, if
the last argument is any negative number, the limit is calculated from the
left so that limit(x^2,x,3,-5) would calculate the limit from the left.
The bug is that limit(x^2,x,3,-1/2) will produce a result that (in pretty
print) indicates a right hand limit. The limit itself is correct. Only
the displayed notation is wrong. Of course, all three of the above limits
are the same, but the statements are valid even when the results are all
different. Try using floor(x) as the expression. floor(x) is the greatest
integer function on the 92. All limits are calculated correctly, but the
left limit is displayed incorrectly as a right limit.
Regards,
Jerry
jerry_thornhill@sw.cc.va.us
Southwest Virginia Community College
Box SVCC
Richlands, VA 24641-1510
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