MathNet 2017-part-04 — 176 problems (EN–VI) Question 73

Suppose $a$, $b$, and $c$ are the sides of a triangle opposite angles $\alpha$, $\beta$, and $\gamma$ respectively. If $\cos \beta \lt 0$ and $\cos \alpha \lt \cos \gamma$, arrange $a$, $b$, and $c$ in increasing order.