prologues := 1; input fichierps; InitFichierPS(-205,-15,215,185); pair A,B,C,D,P,N[],M,I; u := 2cm; A = (0,0); B = (3,0) scaled u; C = (3,3) scaled u; D = (0,3) scaled u; I = 0.5[A,C]; path d; defaultfont := "putri8a"; for i=0 upto 100: beginfig(i+1); draw (2.2[C,D])--(1.2[D,C]); draw D--A--B--C; dotlabel.top("D",D); dotlabel.top("C",C); dotlabel.bot("B",B); dotlabel.bot("A",A); if i<=50: P := (3,3*i/50) scaled u; else: P := (3,6-3*i/50) scaled u; fi; N[i] = whatever * (P rotated 90); N[i] = whatever [C,D]; dotlabel.rt("P",P); dotlabel.ulft("N",N[i]); draw N[i]--A--P--cycle; M := 0.5[P,N[i]]; drawarrow B--P withpen pencircle scaled 1.5 withcolor 0.4blue; if i=0: d := M; else: d := d -- M; drawarrow d withpen pencircle scaled 1.5 withcolor red; fi; dotlabel.bot("I",I); endfig; endfor; end