Show that if \(\vert \alpha \vert < r < \vert \beta \vert\) , then
\[ \int _ { \gamma } { \frac { 1 } { ( z - \alpha ) ( z - \beta ) } } = { \frac { 2 \pi i } { \alpha - \beta } } \]
where γ denotes the circle centered at the origin, of radius r, with positive orientation.