tan$m (2) --- calculate tangent                          04/27/83


          | _C_a_l_l_i_n_g _I_n_f_o_r_m_a_t_i_o_n

          |      longreal function tan$m (x)
          |      real x

          |      Library: vswtmath (Subsystem mathematical library)


          | _F_u_n_c_t_i_o_n

          |      This  function  calculates  the  tangent  of the angle whose
          |      measure is given (in radians) as the argument to  the  func-
          |      tion.   The  arguments  must  have an absolute value of less
          |      than 13176794.0.  The condition SWT_MATH_ERROR$ is signalled
          |      if  there  is  an  argument  error.   An  on-unit   can   be
          |      established  to  deal  with this error; the SWT Math Library
          |      contains a default handler named 'err$m' which the user  may
          |      utilize.  If an error is signalled, the default return value
          |      will be zero.

          |      This  function  is  intended  to serve as a single precision
          |      function although it returns a double precision result.  The
          |      function has been coded so that any value returned will  not
          |      overflow  or  underflow  a  single  precision floating point
          |      value.  The double precision register  overlaps  the  single
          |      precision register so it is possible to declare and use this
          |      function as simply a "real" function.


          | _I_m_p_l_e_m_e_n_t_a_t_i_o_n

          |      The  function  is  calculated  based on a minimax polynomial
          |      approximation over a reduced  argument.   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).


          | _C_a_l_l_s

          |      dint$p, Primos signl$


          | _S_e_e _A_l_s_o

          |      cot$m (2), dint$p (2), dtan$m (2), err$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











            tan$m (2)                     - 1 -                     tan$m (2)