condi := [p1 + p2 + p3 = 1];
simplify(s, condi);
                  condi := [p1 + p2 + p3 = 1]

 /      c (-1 + p1 + p2)        c (-1 + p1 + p2)         
{ a = - ----------------, b = - ----------------,           c = c, 
 \             p1                               p2                

      c (p1 + p2) (-1 + p1 + p2)           c (p2 - 1)          c (p1 - 1)
  d = --------------------------,             e = ----------, f = ----------
                p1 p2                                       p1                 p2    

  \ 
   }
  / 

assigne(%);
c := 10;
a := factor(simplify(a, condi));
b := factor(simplify(b, condi));
d := factor(simplify(d, condi));
e := factor(simplify(e, condi));
f := factor(simplify(f, condi));
                            c := 10

                             a := a

                             b := b

                             d := d

                             e := e

                             f := f

NULL;
Why "factor" does not play its role ?   Thank you.

dr := draw([Tr(t3), AP(cbl), BP(cbl), CP(cbl)]),
textplot([coordinates(A)[], "A"], [coordinates(B)[], "B"], [coordinates(C)[], "C"], align = {above, right});
Error, (in plots:-textplot) unexpected options: [[0, 0, "B"], [13, 0, "C"]]
Why the coordinates are unrecognized ? Thank you.

xA := 4;
yA := 10;
xB := 0;
yB := 0;
xC := 13;
yC := 0;
Mat := matrix(3, 3, [xA, xB, xC, yA, yB, yC, 1, 1, 1]);
phi := (x, y) -> 1/Mat &x [x, y, z];
phi(4, 18/2);
phi(4, 10);
phi(13, 0);
Why the results are not calculated ? Thank you.

how to write the elements of the triangle of Pascal so that all 1 are aligned on a same vertical. Thank you.

restart;
with(geometry);
with(plots);
_EnvHorizontalName = 'x';
_EnvVerticalName = 'y';
point(A, -3, 9);
point(B, -5, 0);
point(C, 6, 0);
xA := -3;
yA := 9;
xB := -5;
yB := 0;
xC := 6;
yC := 0;
triangle(ABC, [A, B, C]);
midpoint(M2, A, C);
midpoint(M1, B, C);
midpoint(M3, A, B);
coordinates(M1);
coordinates(M2);
coordinates(M3);
segment(sA, [A, M1]);
segment(sB, [B, M2]);
segment(sC, [C, M3]);
centroid(G, ABC);
midpoint(J1, A, G);
midpoint(J2, B, G);
midpoint(J3, C, G);
coordinates(J1);
coordinates(J2);
coordinates(J3);
zA := xA + yA*I;
zB := xB + yB*I;
zC := xC + yC*I:
diff((z - zA)*(z - zB)*(z - zC), z)*I;);
allvalues(%, z)
;I am trying to find focus of Steiner ellipse with Marden's theoreme. Thank you.