Question 159
In a triangle $ABC$, the angle $BEC$ is acute, where $E$ is the midpoint of $AB$. On the ray $EC$, choose a point $M$ such that $\widehat{BME} = \widehat{ECA}$. Denote by $\alpha$ the measure of the angle $BEC$. Find the ratio $\frac{MC}{AB}$ in terms of $\alpha$.