Cas bugs in the evaluation of the logarithm?

In summary, the conversation discusses evaluating ln(f(x)) in a computer algebra system for a function f(x) where x is a zero of f(x). The result is expected to be -∞, but it can sometimes give different outputs depending on the function and may not be accurate due to rounding errors. It is important to be cautious when relying on computer calculations.
  • #1
ilario980
35
3
hi,

can you evaluate [tex]ln(f(x))[/tex] in your favorite cas (where x is a zero of f(x) )? what is the result?
 
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  • #2
Welcome to PF!

Hi ilario980! Welcome to PF! :wink:
ilario980 said:
hi,

can you evaluate [tex]ln(f(x))[/tex] in your favorite cas (where x is a zero of f(x) )? what is the result?

If f(x) < 0, then ln(f(x)) isn't defined.

Other than that, the limit of ln(f(x)) will be -∞. :smile:
 
  • #3
yes, i know; but what seems to me strange is that i tryed in some cas to evaluate that value and the ouput is not -inf and is different depending on the function f(x)

after this experience i believe that trust cas may be dangerous...

I.M.
 
  • #4
ilario980 said:
yes, i know; but what seems to me strange is that i tryed in some cas to evaluate that value and the ouput is not -inf and is different depending on the function f(x)

Hi I.M.! :smile:

(btw, it's case, not cas :wink:)

Did you evaluate it using a calculator?

When you get near 0 or ∞, a calculator can give rounding errors that make a lot of difference!
 
  • #5
He means "computer algebra system," or CAS.

- Warren
 
  • #6
chroot said:
He means "computer algebra system," or CAS.

- Warren

ah! :redface:

thanks, Warren! :biggrin:​
 
  • #7
hi Tiny-Tim,
i was not playing with my calculator keys :smile:
i was interpreting (superficially, i admit) some data and this behavior was leading me to an erroneous conclusion


Ilario M.
 
  • #8
Another reason to not trust computers too much.
 

1. What are Cas bugs and how do they affect the evaluation of the logarithm?

Cas bugs are programming errors that occur in the Cas system, a computer algebra system commonly used in scientific and mathematical calculations. These bugs can cause incorrect results when evaluating complex mathematical functions like the logarithm.

2. Are Cas bugs common in the evaluation of the logarithm?

Cas bugs in the evaluation of the logarithm are not very common, but they can occur if the software has not been properly tested or if the input values are outside of the expected range.

3. How can I identify if my logarithm calculation is affected by a Cas bug?

If you are using a Cas system and notice that your logarithm results are incorrect or unexpected, there is a possibility that a Cas bug is causing the issue. It is important to check the software's documentation or contact the developer for assistance in identifying and resolving the issue.

4. Can Cas bugs be fixed or avoided when evaluating the logarithm?

Cas bugs can be fixed by updating the software to a newer version or by using alternative programming methods to evaluate the logarithm. However, it is always recommended to thoroughly test any mathematical calculations to ensure accurate results.

5. How can I report a Cas bug related to the evaluation of the logarithm?

If you encounter a Cas bug while evaluating the logarithm, you can report it to the software developer or community for further investigation and resolution. Providing detailed information about the bug, such as input values and expected results, can help in finding and fixing the issue more efficiently.

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