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Old 2020-11-03, 13:58   #13
Dr Sardonicus
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Feb 2017

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Originally Posted by bhelmes View Post
For mathematical curosity and practical use:

Is it possible to calculate the square root of a quadratic residium by using the tangens function ?
I am unaware of any such method.

For primes p congruent to 1 (mod 4) I don't know of any faster way than factoring x2 - r over the finite field with p elements. In Pari-GP sqrt(Mod(r, p)) will return the square root in (0,p/2) if p is prime and r is a quadratic residue (mod p).
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