/* functions for computing fixed points ;   */ 
give_beta(_c):= (1+sqrt(1-4*_c))/2 $  /* maxima sqrt can handle negative numbers */
give_alfa(_c):= (1-sqrt(1-4*_c))/2 $ 
xMax:1;
xMin:-1.39;
yMin:-1;
yMax:2; 
/* root points */
p_pts:[-0.75,0.25];
py:[yMin,yMin];
/* centers of hyperbolic components of F1/2 family ( on real axis) */
centers:[0]; /* periods: 1 */
cy:[yMin];
load(draw);
draw2d(
 user_preamble="set border 3",
 terminal = png,
 file_name="fixed",
 pic_height= 1000,
 pic_width= 1000,
 title       = "fixed z-points for c along horizontal axis  for fc(z)= z*z +c ",
 ylabel     = "z-point",
 xlabel     = "c-coefficient",
 /* yrange = [yMin,yMax],
 /* period 1 */
 key    = " beta",
 color  = red,
 explicit(give_beta,x,xMin,xMax),
 key    = " alfa",
 color  = blue,
 explicit(give_alfa,x,xMin,xMax),
 /* grid and tics */
 xtics      = {-2,-1.25,-1,-3/4,0,0.25}, 
 /* -2,root points,centers, 0 */
 /*xtics_axis = true,  plot tics on x-axis */
 xtics_rotate = true,
 ytics      = {-2,-1,-0.5,0,0.5,1,1.5,2},
 grid       = true, /* draw grid*/
 /* special points */
 point_type    = filled_circle,
 point_size    = 1.5,
 points_joined = false,
 color         = black,
 key           = "parabolic points",
 points(p_pts,py),
 color         = red,
 key           = "centers",
 points(centers,cy)
)$

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