Lets say f(r) = ln(r):
There are two ways we can write the derivative of f(r):
Since f(r) = ln(r):
By using the quotient rule:
By using the power rule:
Now let's raise e to the power of both sides:
Since e^ln(a) = a:
Let 1/h = k and let 1/r = x, this means if h -> 0, then k -> ∞:
