csqrt() computes the square root of a complex number, x + iy.
    The root is chosen so that the real part of csqrt(x,y) is greater
    than or equal to zero.

                           Entry-Point Names

    Generic                               Compaq
    Function   Data Type   OpenVMS        Tru64 UNIX
    Name       Required    Alpha          Alpha

    csqrt      S_FLOAT     math$csqrt_s   csqrtf
               T_FLOAT     math$csqrt_t   csqrt
               X_FLOAT     math$csqrt_x   csqrtl
               F_FLOAT     math$csqrt_f
               G_FLOAT     math$csqrt_g