datn$m (2) --- calculate double precision inverse tangent  04/27/83


          | _C_a_l_l_i_n_g _I_n_f_o_r_m_a_t_i_o_n

          |      longreal function datn$m (x)
          |      longreal x

          |      Library: vswtmath (Subsystem mathematical library)


          | _F_u_n_c_t_i_o_n

          |      This  function  calculates  the inverse tangent of an angle.
          |      The argument to the function is the tangent  of  the  angle,
          |      and  the  function  returns  the  measure  of  the angle, in
          |      radians.  The function will not signal any errors  based  on
          |      input values.


          | _I_m_p_l_e_m_e_n_t_a_t_i_o_n

          |      The function is implemented as a rational approximation on a
          |      modified  argument  value.  It is adapted from the algorithm
          |      given  in  the  book  _S_o_f_t_w_a_r_e  _M_a_n_u_a_l  _f_o_r  _t_h_e  _E_l_e_m_e_n_t_a_r_y
          |      _F_u_n_c_t_i_o_n_s by William Waite and William Cody, Jr.  (Prentice-
          |      Hall, 1980).


          | _S_e_e _A_l_s_o

          |      atan$m (2), err$m (2),
          |      _S_W_T _M_a_t_h _L_i_b_r_a_r_y _U_s_e_r_'_s _G_u_i_d_e




























            datn$m (2)                    - 1 -                    datn$m (2)