%% auteur : gh %% conique_ellipse_bifocale.jps 1000 setwidth 600 setheight -2.5 2.5 setxrange -1.5 1.5 setyrange /O {0 0} def /a 2 def /b 1 def /c {a 2 exp b 2 exp sub sqrt} def /F {c neg 0} def /F' {c 0} def /Dx {a 2 exp c div neg 0} def /Dx' {a 2 exp c div 0} def /D {Dx Dx 0 1 addv} def /D' {Dx' Dx' 0 1 addv} def /X {Cos a mul} def /Y {Sin b mul} def traceaxes axesarrow $$O$$ O [3 dup] dltexlabel 6 setlinewidth rouge 0 pi 2 mul settrange {X} {Y} courbeparam 3 setlinewidth continu bleu [F F'] points $$F$$ F [3 dup] dctexlabel $$F'$$ F' [3 dup] dctexlabel noir $a$ a 0 [3 dup] urtexlabel $b$ 0 b [3 dup] urtexlabel 3 setlinewidth /t {pi 3 div} def /M {t dup X Y} def noir $M$ M [3 dup] urtexlabel vert F M (-) line F' M (-) line