smc

The measure of each angle, in degrees, of an $n$-sided regular polygon is $\frac{(n-2)180}{n}$. Hence, the two base angles of each triangle formed measure $180-\frac{(n-2)180}{n}$ degrees, and the vertex angle measures $180-2\left(180-\frac{(n-2)180}{n}\right)$ degrees. This simplifies to $\frac{180n-720}{n}$, or $\boxed{\frac{(n-4)180}{n}}$.