If I enter the expression
35+42âˆš2
into my graphing calculator and then ask it for the fractional (rational) equivalent it cannot do so. Since the number is irrational it displays the first few decimal digits:
94.39696962
However, if I enter the expression
55+42âˆš2
into the same graphing calculator and then ask it for the fractional equivalent it displays:
37751

330
But this second number I entered is clearly not rational either.
What's going on?
(In reply to
solution by Charlie)
Incidentally I can only get TI84 Plus Silver edition graphing calculators to do this. Not the TI83 or 84+, just the more expensive Silver Edition.
Several of my students have other brands of nongraphing scientific calculator: TI30, Casio, Sharp.
I tried this on all of the calculators that have a rationalize key and none of them made this error.
Add that to the criticism of the overpriced TI graphing calculators.
I'm just finding out this goes further than I thought:
You can actually fool the calculator with A+Bâˆš2 with many values of A,B even if it doesn't exceed 100.
Edited on May 29, 2015, 12:31 pm

Posted by Jer
on 20150529 12:26:22 