40 setxunit
-1.2 3.5 setxrange
-1.2 3.5 setyrange

traceaxes
axesarrow
marks
pi ytick
pi 2 div ytick

/id { setxvar x } def

mixte
xmin xmax {id} Courbe
   /f {
   Arccos
   } def

   /g {
Cos
   } def

pointilles
0 pi {g} Courbe

continu
2 setlinewidth
bleu

-0.99999 0.99999 {f} Courbe

noir