Ti-89 Limit of Integral undefined BUT it is 4 both by hand and Mathematica

In summary, the conversation is about a limit equation being input into a TI-89 Titanium calculator. The equation involves an integral symbol, the value of pi, multiplication symbol, and infinity symbol. The TI-89 gives an answer of "undef" while the answer is 4 when done by hand and using Wolfram Mathematica. The TI-89 also gives a different result for the integral alone compared to Mathematica. When the TI-89 result is limited with Mathematica, it returns -2/5.
  • #1
Tspyros
1
0
I am giving the following input to Ti-89 Titanium:

limit(S((2 x cos(100 x Pi x t)+2 x sin(10 x Pi x t))2 ,t,-t1,t1)/(2 x t1),t1,inf)

where S is the integral symbol, Pi is π = 3.14, x is the multiplication symbol and inf is the infinity symbol

The TI-89 answer is undef

If I do it by hand it is 4 and Wolfram Mathematica with the following input agrees:

Limit[Integrate[(2Sin[10Pit] + 2Cos[100Pit])2, t, -T, T}]/(2*T), T -> Infinity]

Do you see any errors in my TI89 input?

(I have made the same question in the Ti89 subreddit but it doesn't seem to be used by more than 5 people.)

Thank you!

Some more info:

For the integral alone the Ti89 gives:

-20 π T-10 sin(10 π T) cos(10 π T)+sin(100 π T) cos(100 π T))/((25 π)

whereas mathematica gives:

(400 π T - 10 Sin[20 π T] + Sin[200 π T])/(50 π) with the limit again 4 in Mathematica

If I limit the Ti-89 result with mathematica, it returns -2/5
 
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  • #2
Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
 

1. Why is the limit of the integral undefined on the Ti-89 calculator?

The Ti-89 calculator uses a numerical method to approximate the value of the integral, rather than solving it analytically. This can lead to slight discrepancies and result in an undefined limit.

2. How accurate is the Ti-89 calculator in calculating integrals?

The Ti-89 calculator is generally quite accurate in calculating integrals. However, it is important to keep in mind that it uses numerical methods and may not always provide an exact answer.

3. Why is the limit of the integral 4 when calculated by hand and on Mathematica?

When calculating integrals by hand or on Mathematica, the exact analytical solution is being found. This can result in a more precise answer compared to the numerical approximation used by the Ti-89 calculator.

4. Can the Ti-89 calculator be used to find the exact limit of an integral?

No, the Ti-89 calculator is not capable of solving integrals analytically. It can only approximate the value using numerical methods.

5. Are there any other factors that can affect the accuracy of the Ti-89 calculator in calculating integrals?

Yes, the accuracy of the Ti-89 calculator can also be affected by the function being integrated, the interval of integration, and the step size used in the numerical method. It is important to adjust these parameters for a more accurate result.

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