f(x) = If[x ≤ 0, 0]
g(x) = If[x > 4, x - 2]
h(x) = If[0 ≤ x ≤ 4, x / 2]
a = 2.54 (slider from 0 to 4, step 0.05)
A: (a, h(a))
i = Tangent(A, h)