C

f(x) = 4 / (exp(x) + 1)
a = 0.9 (slider from 0 to 5, step 0.1)
M: (a, f(a))
P: (a, 0)
O = (0, 0)
Q: (0, f(a))
poly1, o, p, m, q = Polygon(O, P, M, Q)
Textepoly1: "Aire " + (Name[O]) + (Name[P]) + (Name[M]) + (Name[Q]) + " = " + poly1