8.1.5 Straight Line



  \begin{texgraph}[name=Droite,export=pgf]
  view(-5,5,-5,5),Marges(0,0,0,0),
  size(7.5),
  F:=sqrt(7), F’:=-F, {foyers}
  Width:=1, Color:=darkgray,
  for t from -pi to pi step 0.1 do
   M:=4*cos(t)+3*i*sin(t),
   Vn:=(M-F)/abs(M-F)+(M-F’)/abs(M-F’),
   Droite(M,M+Vn),{normal to the ellipse}
  od,
  Width:=8, Color:=red,
  Ellipse(0,4,3),
  LabelDot(F,"$F$","S",1),
  LabelDot(F’,"$F’$","S",1)
  \end{texgraph}

 PIC



Evolute of an ellipse