Proof Big Theta (sum of a geometric) Here sum of a geometric, where c is a positive real number.

$g(n)=1+c+c^2+...+c^n$

$\theta(1)$ if $c&lt;1$

Any idea to solve this?
It is known that
$$
1 \leq g(n) &lt; \sum_{m=0}^\infty c^m = \frac{1}{1-c}.
$$
You take it from here.