74 If $0<\alpha, \beta<\frac{\pi}{2}$, and $\sin (\alpha+\beta)=2 \sin \alpha$, then the relationship between $\alpha$ and $\beta$ is
$74 \beta>\alpha$. Since $2 \sin \alpha=\sin (\alpha+\beta) \leqslant 1$, it follows that $\sin \alpha \leqslant \frac{1}{2}, \alpha \leqslant \frac{\pi}{6}$. Also,
$$
\sin (\alpha+\beta)=2 \sin \alpha>2 \sin \alpha \cos \alpha=\sin 2 \alpha,
$$

and $2 \alpha < \alpha + \beta$, thus $\beta>\alpha$.