y=ln(x)

y'=\frac{1}{x}

con \; x>0

f(x) = ln(x)
a = 0.72 (slider from 0.1 to 3.5, step 0.01)
A: (a, f(a))
t = Tangent(A, f)
m = Slope(t)
D: (a, m)
O: (0, 0)
B = (2, 0)
g = Ray(O, B)