Cho ΔABC, BC-12cm,

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$$\begin{gathered} \mathrm{Bài} 1: \mathrm{Cho} ∆\mathrm{ABC}, \mathrm{BC}=12\mathrm{cm}, \overbrace{\mathrm{B}}=60°,\overbrace{\mathrm{C}}=40°. \mathrm{Tính} \\ \mathrm{a}) \mathrm{Đường} \mathrm{cao} \mathrm{CH} \mathrm{và} \mathrm{cạnh} \mathrm{AC} \\ \mathrm{b}) \mathrm{S}∆\mathrm{ABC} \end{gathered}$$

giải giúp mik vs ak