Approximations of numbers are no longer equivalent

Staci Applegarth shared this problem 10 months ago

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In older versions of Geogebra, approximations (rounded values) of fractions were equivalent. However, now that I have updated older applets do not work. Works when the decimals are exact (1/2) but not when rounded (1/3). I have my rounding set to two decimal places currently, but it still isn't considering them the same. Example: https://www.geogebra.org/m/smGkFuFd

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Comments (6)

mathmagic ● 10 months ago

change expressions like a==b with abs(a-b)<=0.001 ie

In older versions of Geogebra, approximations (rounded values) of fractions were equivalent

I do not remember this issue

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Staci Applegarth ● 10 months ago

Thank you for the idea!! I could go back and change them but I have a lot of applets, so to go back and change every single equality that worked before seems out of line. I use your inequality on new ones, but I would like my older versions to continue to work...

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Michael Borcherds ● 10 months ago

I think it's more likely that there's an error in your logic - I think you can simplify this significantly

ch ≟ 0 ∧ r ≟ 1 ∧ d ≟ a_1 ∧ e ≟ a_2 ∨ ch ≟ 0 ∧ r ≟ 2 ∧ d ≟ a_1 ∧ e ≟ a_2 ∨ ch ≟ 0 ∧ r ≟ 1 ∧ e ≟ a_1 ∧ d ≟ a_2 ∨ ch ≟ 0 ∧ r ≟ 1 ∧ e ≟ a_1 ∧ d ≟ a_2 ∨ ch ≟ 0 ∧ r ≟ 3 ∧ g ≟ true

for example define check(x)=abs(ax+b)-c and then

correct = check(ans1)==0 && check(ans2)==0

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Staci Applegarth ● 10 months ago

As I said, all of my logic worked fine up until I went back and tested it this week because I was having issues in creating new material. The problem is that if a=1/6 (which it approximates to 0.17) and a student types in b=1/6 (which also gets approximated to 0.17), it does not count a=b as true. This was not an issue in any materials I created before this last week, so I'm assuming it is an error in the update.

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Michael Borcherds ● 10 months ago

Thanks, I see. That has changed (quite a while ago though). The simplest solution is to change the Input Boxes to the new "Symbolic" ones in Settings -> Algebra https://www.geogebra.org/m/dcek3wcq

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Staci Applegarth ● 10 months ago

Ok, I will try that. Thank you.

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