b = 0 (slider from -10 to 10, step 0.1)
a = 0 (slider from -10 to 10, step 0.1)
B: (2, b)
D: (a, 5)
A: (a, b)
C = (2, 5)
Flächeninhalt, c, d, e, f = Polygon(A, B, C, D)