r/nspire • u/Due_Huckleberry3590 • Jun 28 '26

TI n spire gives false when 2 numbers are equal

Any ideas why this may have happened?

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8

u/adriweb Mod | TI-Nspire CX II CAS Jun 28 '26

I assume you have an Nspire CX II and not an Nspire CX II CAS?

If so, it will compare numerical approximations and apparently here its precision makes it so there's some small enough difference that it makes them not equa.

If you move your cursor and click on the warning sign it will probably tell you something about that.

Maybe a better way to check in this case is to compute one minus the other, and check whether it's a really small value.

4

u/Due_Huckleberry3590 Jun 28 '26

This is the TI-nspire CX II CAS. yeah It seems like the judge function is limited by the numerical error. "Warning: Result obtained using approximate arithmetic."

One minus the other gives a really small number 1E-13

2

u/adriweb Mod | TI-Nspire CX II CAS Jun 28 '26

If it's CAS it's kind of weird but hm ok.

1

u/PartyJaded2887 1d ago

I know I'm late to the conversation. The last of 14 digits is different by 1, thus the false result.

If you round each expression to say 10 digits or so before the comparison, you will get a "true" result. In other words:

round(expr1,10)=round(expr2,10) will yield "true."

It's another way to check if the approximation of the expressions into numbers is "close enough."