Chứng minh BH = AB/2

$$\begin{gathered} ∆\mathrm{ABC} \mathrm{có} \angle \mathrm{H}=90 \mathrm{độ} \\ \angle \mathrm{BAH}=30 \mathrm{độ} \\ \mathrm{C}/\mathrm{m}: \mathrm{BH}=\mathrm{AB}:2 \end{gathered}$$