Originally Posted by

**Siron** It means equivalent to ... take for example:

$\displaystyle \ln(e)=1 \Leftrightarrow e^{1}=e$

It's an equivalence, because

If $\displaystyle \ln(e)=1$ then $\displaystyle e^{1}=e$, worded in mathematical symbols: $\displaystyle \ln(e)=1 \Rightarrow e^1=e$, but also

If $\displaystyle e^1=e$ then $\displaystyle \ln(e)=1$, worded in mathematical symbols: $\displaystyle \ln(e)=1 \Leftarrow e^1=e$

So:

$\displaystyle \ln(e)=1 \Leftrightarrow e^1=e$

But can you solve the equation now? What's your solution now?