@fermatslibrary
Fermat's Library
6 years
Here's a quick method to calculate the square root of a number (√y) by hand
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Replies

@MarioBecroft
CircusMario
6 years
@fermatslibrary Looks like damping the function f(x) = sqrt(x) so it converges, then iterating to find the fixed point. A fundamental technique taught early in #sicp 🙂 (fixed-point (average-damp (...)) See:
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@Cosmic_Bitflip
CosmicBitflip — e/acc
6 years
@fermatslibrary Here is another useful trick: Take whatever method works best for you und approximate every square root before you use the calculator. That way you get the necessary practice and it will come in really handy once you got the hang of it ;)
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@willis_cap
Willis Cap
6 years
@fermatslibrary @mewelch11 suing these guys for copyright infringement
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@stuart_rowlands
Stuart Rowlands
6 years
@fermatslibrary 1. Try to remember this method 2. Fail, ask Siri 3. Grab a calculator while waiting for a response and yep ok Siri says I found this on the web for “where is the square root of pants lasagna”
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@OhMadhu
does all of this matter, these words?
6 years
@fermatslibrary i say another simple method. . take approx squre root of 17 i. e 4 . . Divide 17/4 = 4.25 . then take avg of 4.25 and 4, u will get 4.125 simple?
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@mmammel
Max Mammel
6 years
@fermatslibrary Newton-Raphson FTW
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@KGCiantar
Keith George
6 years
@fermatslibrary This is also known as the Newton-Raphson Method. In this case, f(x) = x^2 - 17, f'(x) = 2x and the x0 = 4.
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@FCIwithAttitude
Straight Outta Compost
6 years
@fermatslibrary when I need to, I just add to x the result of 1 divided by the difference of the power of x and x+1 and then multiplied by the difference between x and y. Sqrt(20): 4+4*[1/(25-16)] = 4+4*(1/9) = 4.444 Of course, the bigger the number the finest the results
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@ranjanpsingh2
Ranjan Singh
6 years
@fermatslibrary This is the method that mathematicians would devise ‘from first principles’; however, I once saw a method that looked like long division which I think is more user friendly.
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@lal_shiban
Shiban Lal Pandita
6 years
@fermatslibrary use a calculator. No y do u require root 17? @monsoon0 @Meetasengupta
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@Chekri_
Siva Prasad Chakri
6 years
@fermatslibrary That's called Newton- Raphson method
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@ramriot
🤖 418: Quinta Venti Latte?
6 years
@fermatslibrary This is also half of the Newton iteration method which if you collect enough public keys from devices can quickly crack the weak keys where any two share the same prime factor. Hint, never trust a cheap embedded device to generate secure RSA key-pairs.
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@ftandru
F. Thomas Andru
6 years
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@MarkVirag
Mark Virag
6 years
@fermatslibrary I remember learning this in school (since forgotten) written out like long division.
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@DEG_Arch
David Garner🦚
6 years
@fermatslibrary Awesome. Wish I had this when I had to do square roots by hand in high school.
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@idrsln
Sorenila
6 years
@fermatslibrary ☝️☝️☝️ you're welcome, atau udah tau? @asardeni
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@rahulraico
Rahul Rai
6 years
@fermatslibrary @elonmusk but the quickest method is to use the calculator 😂
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@Desi_Insaan
Desi Insaan
6 years
@fermatslibrary Why not simply follow the long division method which provides accurate answers to as many decimals as you’d want? Incidentally, the steps are similar as well.
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@JWSBayes
John W Stevens
6 years
@fermatslibrary I was taught how to calculate a square root exactly in the first year of my secondary school. #1971
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