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kkjb
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Solved!

hp prime ——Truncation( or not?) error of root result

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hp.PNG

just like the pic above 

after transform the root form to the Decimal form 

the answer cannot be transformed to the root number form

why does this happened?

My Casio Fx-991CN X can trans root and decimal form back and forth  for many times

So, it's there is a solution to solve this problem 

my firmware version is 20170710

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Jan_D
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The command exact always returns a fraction of 2 integers, so never a root.

For a description of exact,  press Toolbox key (B key), next in the menu press Catlg, select exact, Press Help key.

 

Besides, the answer 978122/564719 is in fact better than root(3), because 

978122/564719=1.7320508075698...

and root(3)=           1.7320508075689...

 

 

 

When you want a root instead of a fraction you could write:

2017-11-11 17.09.36.jpg

 

 

kkjb
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Thank you very much, though I still do not understand the logic of the  function, but your answer solved my problem.
I may use hp prime and casio fx-991cn in different situations.
Thank you very much

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calcpeace
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Hello kkjb,

 

it is a kind of philosophy of implementation.

 

A root cannot be displayed exactly as decimal number, so if you display (and transform) a root as decimal number (let's say with 10 digits), there is no way for return (when there is no place for storing the original root input).

 

When you key in the approximation (with ten digits) and you perform an "exact" command and you get the root, then it is intellectually not honest, because it is a calculator guess, maybe a guess you wish. But it is a lack of infintiy number of digits to give prove of root.

 

Sincerely

calcpeace

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cyrille
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Hello,

 

A phylosophical question is the best way to describe this.

Phylosophes actually have worked a lot on this question:

 

If I am right, but for the wrong reasons, am I still right?

 

Look for the "Gettier problem" for more information on this.

 

Cyrille

I am an HP Employee
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