Re: LF: RE: Math Question, possible ROM error..?


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Re: LF: RE: Math Question, possible ROM error..?



Daniel A. Rachels, Sr. wrote:
> 
> My TI-92 (ROM1.4) gives the following results:
> limit(sqrt(x-4),x,4) (i.e. from pos infinity to 4) = 0
> limit(sqrt(x-4),x,-4) (i.e. from neg infinity to 4) = Non-real result
> limit(sqrt(x-4),x,0) (i.e. from pos and neg infinity to 4) = Non-real result.
> 
> As far as I know these are the correct results for this problem.
> Hope this helps.  AL Rachels

The answers are correct, but I think you misunderstand the third
argument.  The third argument is the point at which you wish to evaluate
the limit.  There is an optional fourth argument that tells the 92 from
which side you wish to approach the limit.  The second one looks
limit(sqrt(-8)), which is 2i*sqrt(2).  If your mode settings are
"Complex Format"="Real", then the non-real result error is correct. 
Similarly, the third problem gives you limit(sqrt(-4)), which is 2i.  If
you wish to look at different sides of the limit as the function
approaches 4, try the following:

limit(sqrt(x-4),x,4)    <2-sided limit at x=4>
limit(sqrt(x-4),x,4,1)  <1-sided limit at x=4 from right side>
limit(sqrt(x-4),x,4,-1) <1-sided limit at x=4 from left side>

Please refer to page 411 in your manual for further instruction on this
function.

Regards,
Shawn


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