Dreieck im Rechteck

c = -3 (slider from -5 to 0)
a = 1 (slider from 0 to 3)
D = Point(yAxis)
B = Point(yAxis)
F = Point(xAxis)
E: (-5, 3)
v1, a_2, b, c_2, d_1 = Polygon(D, B, F, E)
A: (-5, a)
C: (c, 3)
d1, c_1, a_1, b_1 = Polygon(A, B, C)
Punktv1_1 = PointIn(v1)
Punktv1 = PointIn(v1)
Punktd1 = PointIn(d1)
u: d1 / v1
Textd1: "Flächeninhalt des Dreiecks: A_{Dreieck} = " + d1 + " cm²"
Textv1: "Flächeninhalt des Rechtecks: A_{Rechteck} = " + v1 + " cm²"
Text1: "A_{Dreieck} = " + (LaTeX[u]) + "* A_{Rechteck}"