-1.5 3.5 setxrange -1 3.3 setyrange 50 setxunit 50 setyunit /A {-0.5 0} def /B {2.7 0} def /D {1.8 3} def /M {B D mediatrice} def M A D interdroite /C defpoint B C 2 marked D C 2 marked [B C] ligne [A B D] polygone D B C 0.4 (-) tripointarcarrow C D B 0.4 (-) tripointarcarrow D B C 0.45 (-) tripointarcarrow C D B 0.45 (-) tripointarcarrow gsave pointilles D B A 0.6 (-) tripointarcarrow grestore $a$ 1.6 0.43 [1.8 dup] ultexlabel $b$ -0.52 0.52 [1.8 dup] crtexlabel $c$ 1.1 0.05 [1.8 dup] dctexlabel $a$ 0.8 2.2 [1.8 dup] dctexlabel (A) A [1.5 dup] dltext (B) B [1.5 dup] drtext (C) C [1.5 dup] ultext (D) D [1.5 dup] uctext $\mathrm{Abb.}\, 2$ 1.6 -1 [2.0 dup] ultexlabel