Logarithm Tends to Infinity/Proof 1

Proof
From Natural Logarithm of 2 is Greater than One Half:
 * $\ln 2 \ge \dfrac 1 2$

From the definition of infinite limit at infinity, our assertion is:


 * $\forall M \in \R_{>0} : \exists N > 0 : x > N \implies \ln x > M$.

As $x \to +\infty$, we will restrict our attention to sufficiently large $M$.

From Logarithm is Strictly Increasing:
 * $\ln x$ is strictly increasing.

So, for sufficiently large $M$:


 * $x > 2^{2 M} \implies \ln x > \ln 2^{2 M}$

From the Laws of Logarithms:

Choosing $N = \ln 2^{2 M}$:


 * $\forall M \ge a: \exists N > 0: x > N \implies \ln x > M$

for some $a \in \R$.

Hence the result, by the definition of infinite limit at infinity.