sqrt

Square root.

SYNOPSIS:

double x, y, sqrt();
y = sqrt(x);

DESCRIPTION:
Returns the square root of x.
Range reduction involves isolating the power of two of the argument and using a polynomial approximation to obtain a rough value for the square root. Then Heron's iteration is used three times to converge to an accurate value.

ACCURACY:
                      Relative error:
arithmetic   domain     # trials      peak         rms
    DEC       0, 10       60000       2.1e-17     7.9e-18
    IEEE      0,1.7e308   30000       1.7e-16     6.3e-17

ERROR MESSAGES:

message      condition      value returned
domain         x < 0            0.0