Let $ABC$ be a triangle with $AB = BC$. Prove that $\triangle ABC$ is an obtuse triangle if and only if the equation $$Ax^2 + Bx + C = 0$$has two distinct real roots, where $A$, $B$, $C$, are the angles in radians.
Source: Canada Repêchage 2018/3
Tags: quadratics, geometry
Let $ABC$ be a triangle with $AB = BC$. Prove that $\triangle ABC$ is an obtuse triangle if and only if the equation $$Ax^2 + Bx + C = 0$$has two distinct real roots, where $A$, $B$, $C$, are the angles in radians.