this post was submitted on 17 Apr 2024
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Science Memes

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[โ€“] dankestnug420@lemmy.ml 18 points 11 months ago (3 children)
[โ€“] UnRelatedBurner@sh.itjust.works 29 points 11 months ago (2 children)

Uhm, actually ๐Ÿค“โ˜๏ธ!

Afaik sqrt only returns positive numbers, but if you're searching for X you should do more logic, as both -3 and 3 squared is 9, but sqrt(9) is just 3.

If I'm wrong please correct me, caz I don't really know how to properly write this down in a proof, so I might be wrong here. :p
(ps: I fact checked with wolfram, but I still donno how to split the equation formally)

[โ€“] criitz@reddthat.com 25 points 11 months ago* (last edited 11 months ago) (2 children)

You're correct. The square root operator only returns the principal root (the positive one).

So if x^2 = 9 then x = ยฑโˆš9 = ยฑ3

That's why in something like the quadratic formula we all had to memorize in school its got a "plus or minus" in it: -b ยฑ โˆš...(etc)

Thanks, I haven't connected the dots to that (+-) sign and this problem.

[โ€“] Routhinator@startrek.website 1 points 11 months ago (1 children)

So I checked this on my smartphone first, and thought maybe the software is just shit.. So then I checked it on a Casio scientific calc, and both agree.

-3^2 = -9... And 9 != -9

.... Are all the calculators somehow wrong? What's the math rule I'm forgetting here...

[โ€“] criitz@reddthat.com 5 points 11 months ago (1 children)

I think your calculator is interpreting that as -(3^2) and not (-3)^2

[โ€“] Routhinator@startrek.website 3 points 11 months ago (1 children)

Oh derp. Yep it is.

Was better when calcs had a +/- button.

And I remembered the math rule too.

[โ€“] Routhinator@startrek.website 1 points 11 months ago

GD I am just realizing how long its been since I did math in my head without a programming language..

I should take a math class again or something and refresh that knowledge.

[โ€“] h3ndrik@feddit.de 22 points 11 months ago* (last edited 11 months ago) (1 children)

x^2 = 9

<=>

|x| = sqrt(9)

would be correct. That way you get both 3 and -3 for x.

That's the way your math teacher would do it. So the correct version of the statement in the picture is: "if x^2 = 9 then abs(x) = 3"

Cool! Makes sense to me. Honestly, I've never done it this way, but it's so clean. Love it. Thanks.

[โ€“] Evil_Shrubbery@lemm.ee 13 points 11 months ago

Fund the sqrter!

[โ€“] Kusimulkku@lemm.ee 2 points 11 months ago