cbrt() returns the cube root of x.

                           Entry-Point Names

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

    cbrt       S_FLOAT     math$cbrt_s    cbrtf
               T_FLOAT     math$cbrt_t    cbrt
               X_FLOAT     math$cbrt_x    cbrtl
               F_FLOAT     math$cbrt_f
               G_FLOAT     math$cbrt_g