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/sci/ - Science & Math

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4408984 No.4408984 [Reply] [Original]

I am confused.

I was dicking around with my calculator and I got the square root of a number. When I squared this number is gave me one less than the original but with a .9999999999....... (etc) at the end.

The fuck? Why? Does .99999999...... (etc) count as 1?

>> No.4409006
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4409006

It doesn't; your calculator is broken.

>> No.4409009

Yes. Why else would squaring get the original number like that?

>> No.4410682

You cannot expect the square of a square root of a number to be the original number.

For example sqrt(-4) = 2 but 2^2 =/= -4

>> No.4410687

Are you sure your calculator didn't mean .11111111111111111111.....?

>> No.4410695
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4410695

>> No.4410810

>>4410682

this guy is onto something

>> No.4410811

>>4410682
2i

>> No.4410815

>>4410811

>doesnt know sqrt is bi valued and -2i is also a solution

plebs

>> No.4410829

>>4408984
It does equal 1. Precisely.

That said, conventional calculators are digital machines with limited memory. As such, you shouldn't use them to find exact non-integer values.

>> No.4410831

>>4410682
The square root of minus 4 isn't 2, it's 2i. 2i squared is minus 4.

>> No.4410837

>>4410831
>i
Lol, the real world doesnt run on i's. Stick to what is real bro.

>> No.4410841

>>4410837
Stick to what's real?

Then -4 has no square root and the statement remains false.

>> No.4410843

>>4410837
>the real world doesn't run on i's
>but that's wrong, you fucking retard

>> No.4410844
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4410844

>>4410837
>Doesn't know about electricity
By what sorcery did an amish man get onto 4chan?
Does your computer carry packets via some elaborate combination of steam-powered mail tubes? And who the fuck is your ISP?

>> No.4410923

because your calculator isn't exact enough. i have the same problem, even with my TI calculator (used for higher mathematics in grammar school) and my teacher said that these actually work with a system that does in fact not always round up correctly in its calculations.

most of the times a calculator is exact enough so it doesn't do complete mathematical failures (e.g. 2+2=/=4), but in some cases of more complex calculations there may occur errors like that.
When you see that your calculator says "0.9999999999999999999", it usually means that "1" is the valid solution.

>> No.4411008

let 0.9....=x

10x = 9.9...
10x - x = 9.9 -0.9
9x = 9
x=1
QED 0.999999 = 1

>> No.4411458

>>4410843
You fucking retard. i is just a placeholder for complex numbers until they can moved back into the real number system.

>> No.4411466

>>4411458
>moving back complex numbers into reals

That's not how complex numbers work.

>> No.4411472

I've got a feeling most people have no idea how a number is represented digitally, and the relative strengths and limitations of such.

>> No.4411490

>>4411472
Except OP is obviously a troll. If you take the square root of 1 on a calculator, you will get 1. If you then square it, you will still get 1. OP's error would be more likely with another number.

>> No.4411506

If trolol, meh. If not:

If you have, say, a TI-89, you should have the option to switch modes from approximate to exact. Not sure about earlier calcs.

Decimal representations of numbers have to get chopped off (truncated), rounded, and so on, otherwise they'd be impossible to calculate. There are various reasons why your calculator might decide to display that.

In all likelihood, you squared the decimal representation of the square root out to a certain number of decimal places, resulting in an 'original' number very slightly smaller than what you expected.

Getting something like .999999999 or .6666666667 on a calculator almost always means there was rounding or truncation somewhere.

>> No.4411511

.99999999...... (etc)/ .99999999...... (etc)=1, yes

>> No.4411519

>>4411490
>but with a .9999999999....... (etc)
>at the end.

It's plausible that someone might've taken a square root and then squared the approximate result without realizing there could be a change.

>> No.4411528

>>4411466
i * i = -1

retard

>> No.4411532

>>4411528
i is still imaginary. You cannot simply pull another i out of your ass to make it real.

>> No.4411556

>>4411532
Well no duh, I never said that i wasn't complex. I said that the purpose of i in the real world was to serve as a placeholder until the number can be manipulated into real numbers.

>> No.4411576

>>4411556
Don't you see how your statement is bullshit?

>> No.4411580

>>4411532
how's high school? did jennifer notice you yet?

>> No.4411582

>>4411556
No it isn't. i is short for the element (0,1) of the product space which is commonly known as the "compex numbers".

>> No.4411597
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4411597

>>4411580
>that feel when the only reason for a girl noticing you is because you are creepy

;_;

>> No.4411601

>>4411580
>can't into complex numbers
>spouts inane insults instead

stay classy, /sci/