QuestionQUESTION 7 In the diagram below, $T Q R$ represents three points in a horizontal plane on a sportsfield. PQ represents a vertical flagpole.
The angle of elevation of the top of the pole from R is equal to $\theta \cdot \widehat{\mathrm{T}}=\theta \cdot \mathrm{TQ}=\mathrm{TR}=y$. $\mathrm{QR}=x$ units. $\mathrm{TQ} \mathrm{R}=\alpha$. 7.1 Express $\theta$ in terms of $\alpha$ and show that $\sin \theta=\sin 2 \alpha$ 7.2 Hence, prove that in $\triangle \mathrm{PQR}: \mathrm{PR}=\frac{2 y \cos \alpha}{\cos \theta}$ 7.3 If $\alpha=49^{\circ} ; x=20 \mathrm{~m}$ and $y=15 \mathrm{~m}$, calculate the area of $\Delta \mathrm{TQR}$.