Re: TI-M: Limits


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Re: TI-M: Limits




When x approaches x?!  Sorry, but I do believe that x is always equal to x,
that being one of the basic principles of mathmatics...  That just doesn't
compute.  I think probably the only reason you got an answer (just
speculating since I don't have an 89) would probably be because the variable
x was already defined and it simply used that value for the limit.  On to the
definition... limits are basically predicting the behavior of a function.
Let's use lim (x^2) as x approaches 3 as an example.  (And if I'm wrong,
somebody please correct me since I'm a little rusty)  That would be equal to
8.  That was a really easy one.  A different one that takes a bit more
thought would be lim(tan x) as x approaches pi.  Tan (x) is undefined at pi,
because that would be 0/1, but the limit would be equal to infinity because
that is where the function was headed.  A third example would be the
piecewise function y=x+2 when x>3, y=x^2 when x<=3, taking the limit as x
approaches 3.  Coming from the left, or increasing values of x, the limit
would be equal to 8.  But if you come from the right (decreasing values of
x), it would be 5.  I'm going out on a bit of a limb here because its been
about a year since we learned these in class, but I think I'm right.  Feel
free to blast me if I'm not, though.

Eric Tollefson
CmdrERT01@yahoo.com

Chris R Harrison wrote:

> I was wondering if someone could shed some light on limits for me?  I
> want to know 2 things how to do it by yourself and then how to do it on
> the 89.  So how would you figure a limit out in your head, for example,
> find the limit of f(x)= (x-1)/(x^3-2) when x approaches x.  How do you
> know that it is 1/3?  I get that on the 89, but i want to know how to do
> it without becuase i don't want to get lost in calculus and we are just
> begining limits.  Now how would i get an answer on my calculator, like
> this.  lim (x+1)/(x^3-1) x is approaching 1+(but the positive is a
> superscript)? when i put in my calculator like this
> lim((x-1)/(x^3-1),x,1,positive) i get undef but the answer is supposed to
> be +infinity.  What am I doing wrong?
>
> Chris
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