text: /*
      File:       atan.c
  
      Contains:   For arctan(x)
  
      Written by: GUI
  
      Copyright:  (C) 2017-2020 by GuEe Studio for Book OS. All rights reserved.
  */
  
  
  #include <math.h>
  
  M_FLOAT atan(M_FLOAT x) {
    return (MATH_PI_4 * x - x * (fabs(x) - 1) * (0.2447 + 0.0663 * fabs(x)));
  }
  