Don't use this function on the fx-991EX

The "approximately equal" function (shift =) can produce misleading results if your expression contains "ANS". I highly recommend you use the "S-D" key exclusively when you desire an approximate (decimal) value.
A similar quirk involving "ANS" is explored in this older video:
• TI-36X Pro, SHARP EL-W...

[@russell2952]

The shift ≈ reruns the calculation just as = would. It's exactly what I would expect. I don't see the slightest problem here.

[@scottcollins7513]

Evidently you are not alone, since Casio seems okay with it too. Me, not so much.

[@TheCalculatorGuide]

Yes the sequence needs to be 7/2 = Ans² SHIFT = to get the correct approximation, but as you suggest Scott, most people are just going to automatically go straight to press = as they are so used to it. The SD is then of course the function to use. I agree, it is probably best avoided as most are in the habit of pressing = and then pressing SD to get a decimal approximation.

[@scottcollins7513]

Yes, you are capturing the issue well in this comment. If you are math-savvy you will know how to use it correctly and will know ahead of time if you need approximate or exact. But, the typical user (often a student) may not realize they need approximate until after they receive the exact answer.

[@gioiadelsapere]

This is not a design error, it is just getting misused. If you calculate it once using the normal equal button, it will give you Ans^2=49/4, where Ans=7/2, but if you press the approximation button after pressing the normal equals, the ans variable changes to Ans=49/4, it is like having pressed the normal equals button twice . So, if you had pressed the approximation button from the start, the answer would've been what you would expect. The key is doing what it is supposed to do. The key's difference from the equals button is just that, in advance, it is telling the calculator that the answer should be in decimal, or approximated. Hope this was helpful!

[@scottcollins7513]

What you are saying is correct and makes sense. However, the user does not always know that they are going to want an approximate answer until after they perform the calculation.

[@vladkao.]

The issue here is with the ANS variable, not the approx. equals (≈) - if you press the normal equals (=) then the answer will be the same, it recalculates for ANS. So if you want to have the approximate, you should press approx. equals (≈) right away, instead of the normal equals (=).

[@scottcollins7513]

True. The issue is that you may not realize you need the approximate answer until AFTER you get the exact answer.

[@okaro6595]

@@scottcollins7513 Then you use the S-D.

[@scottcollins7513]

@@okaro6595 exactly! That’s the “right” move.

[@EricChiEric]

That's just because of how the equal key and and works, if you did 7 ÷ 2 and then ans squared and did shift equal you would get the right answer.

[@yukiousuzumi2595]

All calculators I've used do the same. Except Some calculators make it explicit which expression you are evaluating. TI Nspire, for example, always shows each evaluation in a new line, and instead of displaying Ans, it substitutes it with the actual value from the above evaluation.

[@scottcollins7513]

I like the idea of having the number itself always appear. I prefer the way the TI-36X Pro operates in this regard -- I believe they have a superior approach to handling the history of expressions and results. Thanks for comment, Yukio.

[@abather11]

Hi sir, I have a question. What's the difference between the - negative sign and the (-) negative sign?

[@scottcollins7513]

The - key (located just above the = key) is the subtraction key. The (-) key (located just above the STO key) is the negative (sign) key. In some cases they might give you the same result, but you should get used to using the (-) negative (sign) key when you are entering negative numbers and only use the - subtraction key when you are performing the operation of subtraction. Hopefully this helps. It is a subtle, but important distinction, so your question is a very good one.

[@abather11]

@@scottcollins7513 thank you sir, that helps

[@petermikus2363]

This could also be avoided if you sed the aproximation button insted of the = button dont kniw its name in english You did this ans^2=49/4 the hit the aproximation key and considering how thus calculator takes it the whole input you did would be this ans^2=49/4 Now ans equals to (49/4) and then this operation ans^2≈ and you got 150 something you basically asked the calculator to calculato 49/4 to the power of 2 and asked it to give you an anwer from that It should work if you did this instead Ans^2≈12.25 or around that

[@petermikus2363]

Ut is nkt a issue in the calculator if thats the case the issue is how you used the function

[@petermikus2363]

And if thats the case then it would be nice if you could make a one minute video explaining it but as i said it is just a theory

[@scottcollins7513]

What you are saying here makes sense and is correct. However, I had two people (one student and one teacher) who both were thrown off by this -- both recognized that the answer they were getting was wrong, but they did not know why.

[@scottcollins7513]

@@petermikus2363 Agreed. But, many times one does not know they need the approximate answer until AFTER they have the exact answer.

[@petermikus2363]

@@scottcollins7513 i assumed you would know this i was just stating that however i can see how it can be confusing and understand that using the sd key is less confusing

[@okaro6595]

That is not a bug. You should use the approximate instead of =, not in addition to it. If you have the value on display then you should use S-D. However, if you want decimals it is best to set the output mode.

[@scottcollins7513]

I don’t consider it a bug - just a bad idea. I had a teacher and a student confused by it. No need for it when you have the S-D button. And, yes, it is cool that the CASIO lets you set output mode separately from input mode - my SHARP does not permit that.

[@strangnet]

The manual isn't especially explicit about this feature either (p.10): "While MathI/MathO or MathI/DecimalO is selected for Input/Output on setup menu, each press of [SD] will toggle the currently displayed calculation result between its fraction form and decimal form, its √ form and decimal form, or its π form and decimal form." Further down: "To obtain a decimal value calculation result while MathI/MathO or LineI/LineO is selected, press shift + [=] (≈) instead of [=] after inputting a calculation."

[@scottcollins7513]

Good info, Patrick. Thank you.

[@MrMarcec85]

1) thanks 2) well, if there are 2 keys, there must be a difference between the two 3) Casio is used to put a lot of similar key that really baffle anyone who is not super inside not only math itself, but also how IA solve math problems... and it s not very useful for a student or someone that "uses" math but does not go to sleep thinking at 6th dimension graphs.

[@scottcollins7513]

1) You are welcome! Thank you for leaving a comment. 2) Good point! I had never even noticed the function, but in a very short span of time it confused two people. 3) My co-teacher said that the TI-36 feels more like a calculator and the fx-991EX feels more like a computer -- she feels the 991EX is too complicated. I do not find it to be bad, but I'm a calculator nerd (even if I do not dream of 6th dimension graphs!).

[@MrMarcec85]

@@scottcollins7513 I just bought the 991 ex because it was on super sale (14 Euros) only because I have a casio 570A that belonged to my grandpa (with a 300 ex or something like that - when they sold calc with those beautiful flip leather cases!) , and I wanted her "great-grandaughter". I got the mathprint last year, which I consider better, except for the QR function that is very intuitive to see graphs and the inequality solver.

[@aniksajib69]

Make video in comparison of 991 ex vs 991es plus.

[@scottcollins7513]

I actually did something very close - the 991ES is sold as the 115ES in the US, so that’s the one I used in the comparison video w the 991EX.

[@blackberry949]

Is 991ex a programmable calculator?

[@parragoriouse0138]

it is not a programmable calc unfortunately

[@blackberry949]

@@parragoriouse0138 ops l have bought 991ms 2nd edition 🥴🥴

[@gioiadelsapere]

No

[@DazHuang72]

Thank you

[@scottcollins7513]

You are welcome.

[@IO23777]

Clean it! - Look at the state of that Solar cell..

[@scottcollins7513]

Busted.