def emit_atan(no,operand)
no_a1 = no + "_a1"
no_a2 = no + "_a2"
$outfile4.puts "# emit arctan $eq_no = #{$eq_no}"
$outfile4.puts "pr = " + $eq_rec[$eq_no].priority.to_s
$outfile4.puts "k2 = k - pr "
$outfile4.puts no + "[k2] = (ats(k2," + operand + "," + no_a2 + ",2) - " + operand + "[1] * att(k2-1," + no_a1 + "," + no + ",2) - att(k2-1," + no_a2 + "," + no + ",2))/(" + no_a2 + "[1] + " + operand + "[1] * " + no_a1 + "[1])"
$outfile4.puts no_a1 + "[k2] = att(k2-1," + no_a2 + "," + no + ",1)"
$outfile4.puts no_a2 + "[k2] = $minus_one*att(k2-1," + no_a1 + "," + no + ",1)"
return
end