Expression for sum of $n$ exponentials So I have this sum of exponentials and I would like to find an expression for it. 
$$\sum^n_{i=1} e^{\mu(i-1)} $$
Note that $i$ is not an imaginary indicator. I am aware there is a formula for summing a purely exponential sum, but I am not clear as to what happens to the $\mu$. 

The sum $S$ can be rewritten as $$S= \sum_{i=0}^{n-1} e^{\mu i}=\sum_{i=0}^{n-1} (e^{\mu})^i=\frac{1-e^{\mu n}}{1-e^{\mu}}$$ since the geometric series $$\sum_{i=0}^{n-1} x^{i}=\frac{1-x^n}{1-x}$$
