My TI-89 calculators finance app is giving me the wrong answers by a few 1000 or so and increases how far off it is the larger the figure

Make sure you're in the proper angular mode. You can see the angular mode by pressing the MODE key.

Hi danagasta,

If my last instructions did not work then you need to reset your RAM. You are missing the negative sign and, I have no idea where you got the absolute value inside the brackets.
Yes, the absolute value are used in books and, on integral tables but, I can asure you that the Ti 89 should not have produce them in this answer.

I'll stand behind that In( -cos(x) / (sin(x)-1)) is the correct answer. You can go ahead and simplify after the calculation to get the answer you want but, that is the good answer that Ti 89 is going to give you for the integral of sec(x).

Errors that do not match the suspected, I am pretty sure that Texas Instruments would have you clear the RAM. I do not like resetting the RAM but, I could not find the cause to why you got the answer you did. And so far no other expert has produced a solution to convince me otherwise.

I was not able to come up with any of the 3 answers MiB8888 did on my Ti 89. I am not saying that they are not good answers, they are book and integral tables answers. You are not going to get them on the Ti 89.

The Finance App is part of the Operating system. You cannot get rid of it. The other Applications can be deleted from Archive Memory.
To restore them:

1. Download them from education.ti.com
2. Connect calculator to computer
3. Run TI Connect.
4. Drag and Drop an App onto the TI connect Main window
5. The App should transfer to calculator
6. After transferring one or two Apps, Press [2nd][MODE] to (QUIT) and let the calculator defragment the memory.
7. Transfer one or two more Apps.

Here is the link to the latest software page for the TI83/84 Plus software.

Glad to be of help.

Hello,
The answer I gave you was taken verbatim from the TI FAQ and knowledge base. I copied and pasted the part relevant to you calculator.
In any case, I sent an e-mail message to [email protected], giving the link to your original question and my answer to it. I took the liberty to copy/paste your present message. I also asked about that invalid certificate.
All we can do know is wait for their reply.

k24674.

Press the APPS key and select Finance. If there is no Finance entry, then you need to load the Finance app, which you can get from the calculator CD or download from http://education.ti.com

I had the same problem when I got my first 89, even though it's really a feature and not a problem.

Press the diamond key then enter to get your answer, and it will give you the decimal answer instead of the exact answer like you have been getting. Hope this helps...

Hello,
Your TI81 can only perform numerical calculation: It always give uour numbers. The TI89, a more sophisticated calculator, can of course do numerical calculation, BUT ALSO symbolic ones. You ask it for the derivative of sin(x) and it will give you cos(x).
Anyway, if you want a decimal result for you calculation above one of the numbers must have a decimal point (instead of writing 2PI write 2.PI.

The TI 89 can do exact calculations. But if you want approximate results any number in the sequence of operations must have the mark of a decimal. Numbers without decimal marks are considered integers, Integer numbers with a decimal mark are treated as floating point numbers ( meaning decimal).

Hope it clarifies things for you.

Are you using the finance app?

[APPS] [1] [ENTER]

For NPV, choose "7:npv("
Then use:
npv(interest rate, cost {cash flows}, {frequencies of cash flows})

For IRR, choose "8:irr("
Then use:
irr(interest rate, cost {cash flows}, {frequencies of cash flows})

Use the "FINANCE" app:

[APPS] [1] [ENTER]

for npv: select "7:NPV"
now you should get "npv(" on your screen.
use: npv(interest rate, cost {cash flows}, {frequencies of cash flows})


for irr: select "8: irr"
"irr(" will come up.
use: irr(interest rate, cost {cash flows}, {frequencies of cash flows})