TI-89 Differentiation: How to Get Algebraic Derivative and Why Negative Result?

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Discussion Overview

The discussion revolves around the use of the TI-89 calculator for differentiation and the discrepancies in output between the TI-89 and TI-83 calculators. Participants explore how to obtain algebraic derivatives and address issues related to unexpected negative results in trigonometric calculations.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant expresses confusion over receiving a numerical solution instead of the expected algebraic derivative when differentiating x^2.
  • Another participant suggests checking if 'x' is defined as a constant, which could affect the differentiation output.
  • There is a recommendation to ensure the calculator is set to degrees rather than radians to address the negative output for sin(60).
  • A participant seeks guidance on how to revert 'x' back to a variable after it was associated with a number.
  • Another participant provides a method to clear the variable 'x' using the VAR-LINK menu on the TI-89.

Areas of Agreement / Disagreement

Participants generally agree on the importance of ensuring 'x' is not defined as a constant and that the calculator settings are correct. However, the discussion does not reach a consensus on the best method to clear the variable 'x' as participants offer different approaches.

Contextual Notes

Some limitations include the assumption that the calculator settings are correctly configured and that participants may not have access to the calculator to verify steps. The discussion also does not resolve the underlying reasons for the negative output in trigonometric calculations.

Who May Find This Useful

This discussion may be useful for TI-89 users seeking assistance with differentiation and troubleshooting calculator outputs, as well as those comparing functionalities between different calculator models.

Helicobacter
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1. After I launch the "Home" program and enter

d(x^2,x)

The calculator spits out -52.4916, a numerical solution. What I want is the algebraic derivative 2x - how do I get to the algebraic derivative?

2. When I enter sin(60), it gives me -0.304811 as an output. Why does the Ti-89 give a negative result, while the Ti-83 provides me with a positive one?

Sorry if I'm in the wrong forum. The forum search didn't spit out anything.
 
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1. Make sure you don't have x defined as some constant. If you just enter 'x,' what does it return?

2. Make sure the calculator is set for degrees, not radians.

- Warren
 
chroot said:
1. Make sure you don't have x defined as some constant. If you just enter 'x,' what does it return?

2. Make sure the calculator is set for degrees, not radians.

- Warren

Thank you for your feedback, Warren. You are right, I associated a number with x. How can I make it a variable again?
 
Helicobacter said:
Thank you for your feedback, Warren. You are right, I associated a number with x. How can I make it a variable again?

I think there's a menu option, I think second then f1, or maybe f5 will give you the option to clear a-z or maybe it's under the var-link think which would be second then "-". The batteries in my 89 are dead so I can't check which one it is, but I'm pretty sure it's one of those.
 
I have my TI-89 right here, so I'll look. Yep, go to VAR-LINK and scroll down until you see stored items and you should see "x" there. Delete it and you're good!
 

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