Δx

f(x + Δx) - f(x)

f(x) = x^(2) / 4 + 1
P = Point(f)
Δx = 2 (slider from 0 to 5, step 1.0E-4)
Q: (x(P) + Δx, f(x(P) + Δx))
Sekante = Line(P, Q)
F: (x(Q), y(P))
a = Segment(P, F)
b = Segment(F, Q)
Steigung = Slope(Sekante)
Tangente = Tangent(P, f)
Text1: "\frac {\Delta y}{\Delta x} = \frac {f(x+\Delta x) - f(x)} {\Delta x} =\frac { " + (LaTeX[y(Q) - y(P)]) + "}{" + (LaTeX[a]) + "} = " + (LaTeX[(y(Q) - y(P)) / a]) + ""