TI 89 Integral seems wrong.... What am I missing?

• Calculators
• jdcirbo
In summary, the conversation is about the discrepancies in the output of a TI 89 Platinum calculator for the calculation of ln(abs(cos(x))/abs(sin(x)-1)) for the integral sec(x)dx. It is supposed to return ln(abs(tan(x)+sec(x)) or ln(abs(sin(x)+1)/abs(cos(x))), but when x=0 is entered, it gives an "undefined" result instead of 0. The question is whether this is a computation error or a syntax issue with TI Basic. However, the conversation ends with an update that the calculator is now giving the correct output of 0 for x=0.

jdcirbo

My TI 89 Platinum is returning ln(abs(cos(x))/abs(sin(x)-1)) for integral sec(x)dx. It's supposed to return ln(abs(tan(x)+sec(x)) or ln(abs(sin(x)+1)/abs(cos(x))). If you enter x=0, you get 'undefined' the way my TI 89 is doing it. It's supposed to return 0. Is this a computation error or something with the syntax of how TI Basic computes integrals?

Ln(abs(sin(x)+1)/abs(cos(x))) = Ln(abs(cos(x))/abs(sin(x)-1))

And abs sin / abs cos = abs tan

Baluncore said:
Ln(abs(sin(x)+1)/abs(cos(x))) = Ln(abs(cos(x))/abs(sin(x)-1))
I don't understand why I'm getting a "non-real result" from the calculation when I enter x=0. Why is that occurring? It should be the same regardless of which form it's written in.

jdcirbo said:
My TI 89 Platinum is returning ln(abs(cos(x))/abs(sin(x)-1)) for integral sec(x)dx. It's supposed to return ln(abs(tan(x)+sec(x)) or ln(abs(sin(x)+1)/abs(cos(x))). If you enter x=0, you get 'undefined' the way my TI 89 is doing it. It's supposed to return 0. Is this a computation error or something with the syntax of how TI Basic computes integrals?
UPDATE: Just to make me look like a liar... Now my TI 89 is returning 0 for x=0... ? It was returning "Non-real result" before.

Is the battery charge good?

1. Why does my TI 89 calculator give a different answer for an integral than what I calculated manually?

There could be several reasons for this. The most common reasons are: 1) the calculator is using numerical methods to approximate the integral, which may result in a slightly different answer than the analytical solution, and 2) the calculator is using a different integration technique than what you used manually, which could result in a different answer.

2. Is there a way to check if the answer the calculator gives for an integral is correct?

Yes, you can check your answer by graphing the function and its antiderivative on your calculator. If the graphs intersect at the bounds of integration and the areas under the curves match, then your answer is correct.

3. Can I change the settings on my TI 89 to get a more accurate answer for an integral?

Yes, there are certain settings on the calculator that can be adjusted to increase the accuracy of the integral calculation. These include changing the number of intervals used in numerical methods, adjusting the tolerance level, and changing the integration technique.

4. Why does my TI 89 give an error message when I try to calculate certain integrals?

Some integrals cannot be calculated using the standard integration techniques programmed into the TI 89. This could be due to the complexity of the function or the bounds of integration. In these cases, you may need to use a different technique or consult a math expert for assistance.

5. Are there any common mistakes that can cause the TI 89 to give an incorrect answer for an integral?

Yes, some common mistakes include inputting the function or bounds of integration incorrectly, not using proper parentheses or brackets in the input, and not adjusting the calculator settings appropriately for the desired level of accuracy. It is always important to double-check your input and settings to ensure an accurate answer.