-1 1 setxrange -0.3 1 setyrange /A {-0.7 0} def /B {0.7 0} def /M {A B milieu} def /c {A B diamcercle} def 70 c cpoint /C defpoint %A C B angledroit [A B C] polygone [M C] ligne M A C 0.12 (-) tripointarc A C M 0.12 (-) tripointarc C B M 0.1 (-) tripointarc M C B 0.1 (-) tripointarc C B M 0.11 (-) tripointarc M C B 0.11 (-) tripointarc [A B C M] points 0 180 c Cercle (A) A [1.5 dup] dltext (B) B [1.5 dup] drtext (C) C [1.5 dup] uctext (M) M [1.5 dup] dctext $\rm{Abb}.\,7$ 0.15 -0.25 [2.0 dup] ultexlabel $\theta$ 0.31 0.44 [1.6 dup] ultexlabel $\theta$ 0.62 0.031 [1.6 dup] ultexlabel $\phi$ -0.6 -0.02 [1.6 dup] urtexlabel $\phi$ 0.2 0.45 [1.6 dup] ultexlabel