Possible bug with TI-83+?

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Summary:

√(73)^2 ≠ int(√(73)^2) ???

Possible bug with TI-83+?

Purpzie 26 Apr 2018 19:43

√(X)² should equal X, this is a basic rule in math. However, I was messing around and discovered something strange.

1. Put in √(45)² and hit enter.
2. Then, use Ans=int(Ans). The answer should be 1, indicating that the statement above is true.
3. Now, put in √(73)² and hit enter.
4. Using Ans=int(Ans) actually outputs 0, indicating that there is a decimal part to Ans, even though it just displays as 73.

Despite this, using √(73)²=73 still outputs as 1, as intended. This means there must be some sort of bug somewhere.

Quick logic from the calculator that proves that this is a bug:

• 73 = int(73 … true
• √(73)² = 73 … true
• √(73)² = int(√(73)² … FALSE

After this, I made a small program with the intent to find the numbers that can cause this bug.

Ans→X   // Ans is what number to start on
Repeat getKey
Repeat A=0    // Using repeat instead of for, because this needs to continue for as long as possible until it finds a bugged number.
X+1→X
√(X)^2
Ans=int(Ans→A   // Check if number is bugged
End
Disp X   // Display the bugged number
X→L₁(dim(L₁)+1   // Then put it to a list, which we can get later.
End

Here are just a few numbers in the list:
47, 51, 54, 57, 60, 65, 67, 73, 76, 78, 90, 92, 108, 112

Let's say we had a number, B, that could be anything. I was doing this in a program to check if B² was an integer. Because of this bug, I am unable to do so.
If it's actually intended behavior by the calculator, how would I do this in a program to ensure it's correct every time?

Re: Possible bug with TI-83+?

Trenly 26 Apr 2018 19:52

To check if B^2 is an integer, you could use

If fPart(B^2)

As for the bug, I was thinking maybe its something with your os version. Which version are you using?

Re: Possible bug with TI-83+?

Purpzie 26 Apr 2018 19:56

The fpart method doesn't work, it returns the wrong value as before. Instead of the actual fpart, though, it simply returns 1.

How do I get my OS version? Got it, 1.19 on a TI-83+

Edit: I found a way to check for sure.

If fPart(B^2) and fPart(B^2)≠1

Because fPart should always return a decimal or 0, returning 1 means it's a bugged number.
Also, strangely, the 1 it returns also returns 1 if fPart is used on it again.

Last edited on 01 May 2018 15:58 by Purpzie Show more