algorithm for radicals?

[ascii]

does anyone know of an effective way to compute square roots that wont just be brute forcing it by adding a puny decimal like .000000000001 and testing if when squared gives the right number? thank you :)

[Branflakes91093]

like the sqrt function?
http://cplusplus.com/reference/clibrary/cmath/sqrt/

EDIT: And here are some faster implementations (that sacrifice some accuracy for more speed)
http://ilab.usc.edu/wiki/index.php/Fast_Square_Root

[ascii]

haha thank you :)