SI. 3 If $\log _{10} 210+\log _{10} k-\log _{10} 56+\log _{10} 40-\log _{10} 120+\log _{10} 25=p$, find $p$.
SI. 4 If $\sin A=\frac{p}{5}$ and $\frac{\cos A}{\tan A}=\frac{q}{15}$, find $q$.
$\begin{array}{l}p=\log _{10}\left(\frac{210 \times 32 \times 40 \times 25}{56 \times 120}\right) \\ =\log _{10} 1000=3 \\ \sin A=\frac{3}{5} \\ \frac{\cos A}{\tan A}=\frac{q}{15} \\ \frac{\cos ^{2} A}{\sin A}=\frac{q}{15} \\ \frac{1-\sin ^{2} A}{\sin A}=\frac{1-\left(\frac{3}{5}\right)^{2}}{\frac{3}{5}}=\frac{16}{15}=\frac{q}{15} \\ q=16\end{array}$