Question: ellipse in a rectangle

with(geometry):
_EnvHorizontalName := x:
_EnvVerticalName := y:
a := 7:
b := a*(1/2 + 1/6*sqrt(45 - 24*sqrt(3)))^2:
r := b*sqrt(b)/(sqrt(a + b) + sqrt(a)):
point(A, -a, b): point(B, -a, -b):
point(C, a, -c): point(F, a, b):
Sq := square(Sq, [A, B, C, F]):
circle(C1, [point(P1, [r, 0]), r]):
circle(C2, [point(P2, [(1 + sqrt(3))*r, r]), r]):
circle(C3, [point(P3, [(1 + sqrt(3))*r, -r]), r]):
ellipse(E, x^2/a^2 + y^2/b^2 = 1, [x, y]):
solve({Equation(C1), x^2/a^2 + y^2/b^2 = 1}, {x, y}):
point(T, [5.349255162, 2.829908743]):
IsOnCircle(T, C1);
draw([E(color = cyan), C1(color = yellow, filled = true), T(symbol = solidcircle, symbolsize = 20, color = red), Sq, C2(color = red), C3(color = red),Sq(color=blue)], axes = normal, view = [-a .. a, -b .. b], scaling = constrained);
square: (196+(7*(1/2+(1/6)*(45-24*3^(1/2))^(1/2))^2+c)^2)^(1/2)-(196+196*(1/2+(1/6)*(45-24*3^(1/2))^(1/2))^4)^(1/2) = 0
square: (7/2)*(1/2+(1/6)*(45-24*3^(1/2))^(1/2))^2-(1/2)*c = 0
Error, (in geometry:-square) not enough information to define a square
                             false

Error, (in geometry:-draw) cannot determine the vertices for drawing .Why all these errors ? Thank you.

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