-1 6 setyrange
%% rayon du grand cercle
/r 4 def
%% angle definissant le point N
/alpha 60 def
/A {r neg 0} def
/B {r 0} def
/I {A O milieu} def
/c1 {O r} def
/c2 {I r 2 div} def
alpha c2 cpoint /N defpoint
A N c1 interdroitecercle /M defpoint
popp
/T1 {M O M perp} def
/T2 {N I N perp} def
.4 setgray
180 0 c1 Cercle
180 0 c2 Cercle
[A B] ligne
[A M O N] ligne
0 setgray
T1 droite
T2 droite
[I N] ligne
N M O .5 (-) tripointarc
O A N .5 (-) tripointarc
N O A .5 (=) tripointarc
M O N .4 (=) tripointarc
I N T2 exchp popp angledroit
O M T1 exchp popp angledroit
$$
{\cal C} _1
$$
25 c1 cpoint [1.5 dup] texlabel
$$
{\cal C} _2
$$
105 c2 cpoint [1.5 dup] ultexlabel
setTimesItalic
(O) O dctext
(I) I dctext
(A) A dltext
(B) B drtext
(M) M urtext
(N) N uctext
(T) -5 T2 xdpoint urtext
(2) indice
(T) -1 T1 xdpoint urtext
(1) indice