AlastorMoody wrote: Prove that if the angles $\alpha$ and $\beta$ satisfy $\sin(\alpha + \beta) = 2 \sin \alpha$, Then $$\alpha < \beta$$ Are there any other conditions? Otherwise, $(\alpha,\beta)=\left(\frac{7\pi}6,\frac\pi3\right)$ is a counterexample.

Nope the question said that much only