f(x) = 1 / x
g = Function(f, 0, 50)
a = 2 (slider from 0 to 20, step 0.1)
b = Integral(f, a, 2 * a)
c: x = a
d: x = 2 * a
A = Intersect(c, xAxis)
B = Intersect(d, xAxis)
teksti2: "2a(" + (2 * a) + ")"
teksti1: "A = \int_{" + (LaTeX[a]) + "}^{" + (LaTeX[2 * a]) + "}\left(\frac{1}{x}\right) dx=" + (LaTeX[b]) + ""
teksti3: "a(" + (LaTeX[a]) + ")"