(iii) To find angle RQP using the scalar product:

The scalar product is given by:

\(\overrightarrow{PQ} \cdot \overrightarrow{RQ} = 6 \times 2 + 0 \times 6 + 0 \times 3 = 12\).

The magnitudes are:

\(|\overrightarrow{PQ}| = \sqrt{6^2} = 6\).

\(|\overrightarrow{RQ}| = \sqrt{2^2 + 6^2 + 3^2} = \sqrt{49} = 7\).

Using the formula:

\(\cos \theta = \frac{\overrightarrow{PQ} \cdot \overrightarrow{RQ}}{|\overrightarrow{PQ}| \times |\overrightarrow{RQ}|} = \frac{12}{6 \times 7} = \frac{12}{42} = \frac{2}{7}\).

Thus, \(\theta = \cos^{-1}\left(\frac{2}{7}\right) \approx 63.2^\circ\).