zero-point of e-Function

zero-point of e-Function - Messages

#1 Posted: 2/18/2016 4:48:51 AM
mtothaz

mtothaz

0 likes in 8 posts.

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Hello everyone,

I stumbled over a zero-Point Problem...

I attached a Picture of my Problem.

I wanted to calculate the Zero-Point of f(x)=-e^(x/33)+6. The Programm says that there are no "real" Zero Points.
So I played around a Little bit and found out that when the Exponent reaches 0.091 ->0.09 the error occurs.

Do you guys have any guesses or did I found a bug in here?

Thanks

zero_point.JPG
#2 Posted: 2/18/2016 5:30:51 AM
sergio

sergio

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Group: User

It is not a bug. You simply set correctly
Tools--> Options --> Calculation --> Roots (range)

sergio
2 users liked this post
Davide Carpi 2/18/2016 5:44:00 AM, mtothaz 2/18/2016 6:53:00 AM
#3 Posted: 2/18/2016 6:55:39 AM
mtothaz

mtothaz

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Thank you very much!

I am new to the Programm and did not know (and why?) there were an upper and lower range of the roots.

The topic can be deleted..
#4 Posted: 2/18/2016 12:16:55 PM
Jean Giraud

Jean Giraud

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No, don't delete the topic. Answer is correct, it doctored the case.
Some very flat functions may not find roots even in advanced CAS [Computer Algebra System].
Smath 32 bits, not 64 extended floating point does not help either.
More generally, computing machinery are limited by their "ulp" [Unit in Last Place].
"ulp" => read as popular "granularity". Between two machine numbers to close together
the system zigzag eternally, but they all have an internal error detect.
"No real root" is a typical Smath error message.

Jean

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