hypot() computes the length of the hypotenuse of a right
    triangle, where x and y represent the perpendicular sides of
    the triangle.

    hypot(x,y) is defined as the square root of (x**2 + y**2) and
    returns the same value as cabs(x,y).

                           Entry-Point Names

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

    hypot      S_FLOAT     math$hypot_s   hypotf
               T_FLOAT     math$hypot_t   hypot
               X_FLOAT     math$hypot_x   hypotl
               F_FLOAT     math$hypot_f
               G_FLOAT     math$hypot_g