-1.5 1.5 setxrange
-1.5 1.5 setyrange

/C {O 1} def
/d {2 3 div dup 1 exch 2} def
d C interdroitecercle /M2 defpoint /M1 defpoint
/M' {M1 O sympoint} def 
1 3 div dup setquadrillagestep
quadrillage

.7 setlinewidth
tracerepere
marks

gsave
mixte 
d droite
pointilles
[M1 M1 projy] ligne
[M1 M'] ligne
grestore

/arrowscale {1.5 dup} def
/arrowangle -4 def
M1 O M' .5 (->) tripointarc
/arrowangle 4 def
M1 O 1 0 .35 (<-) tripointarc
1.2 setlinewidth
C cercle

[M1 M'] points

<tex>
$${2\over 3}$$
</tex>

/arrowscale {.8 dup} def
/arrowangle 0 def
/A1 {2 3 div 0} def
/A2 {2 3 div 0 .15 .1 addv} def
A1 A2 0 .1 addv (<-) line
A2 urtexlabel

<tex>
$$-{\sqrt 5\over 3}$$
</tex>

/B1 {0 5 sqrt -3 div 0 -.15 addv} def
B1 ultexlabel

setTimes
   (cos) xmax 0 (-10 0) dltext
   (sin) 0 ymax (0 -10) drtext
setTimesItalic
   (O) O dltext
   (M) M1 drtext
   (M') M' ultext
   (a) .37 -.18 cctext
setSymbol
   (p) .35 .35 urtext