Challenging +1.2 This is a straightforward application of the polar area formula requiring students to find the area between two polar curves using integration. While it involves hyperbolic functions (cosh) and requires careful setup of the integral difference, the method is standard for Further Maths students. The final step of dividing by tin coverage and rounding up is routine. The question is slightly above average difficulty due to the Further Maths content and integration of cosh, but follows a predictable template without requiring novel insight.
10 In this question you must show detailed reasoning.
A region, \(R\), of the floor of an art gallery is to be painted for the purposes of an art installation. A suitable polar coordinate system is set up on the floor of the gallery with units in metres and radians. \(R\) is modelled as being the region enclosed by two curves, \(C _ { 1 }\) and \(C _ { 2 }\). The polar equations of \(C _ { 1 }\) and \(C _ { 2 }\) are
$$\begin{array} { l l }
C _ { 1 } : r = 5 , & - \frac { 1 } { 2 } \pi \leqslant \theta \leqslant \frac { 1 } { 2 } \pi \\
C _ { 2 } : r = 3 \cosh \theta , & - \frac { 1 } { 2 } \pi \leqslant \theta \leqslant \frac { 1 } { 2 } \pi
\end{array}$$
Both curves are shown in the diagram, with \(R\) indicated.
\includegraphics[max width=\textwidth, alt={}, center]{7b2bfb4e-524f-4d1c-ae98-075c7fb404f9-6_1481_821_836_251}
The gallery must buy tins of paint to paint \(R\). Each tin of paint can cover an area of \(0.5 \mathrm {~m} ^ { 2 }\).
Determine the smallest number of tins of paint that the gallery must buy in order to be able to paint \(R\) completely.
10 In this question you must show detailed reasoning.
A region, $R$, of the floor of an art gallery is to be painted for the purposes of an art installation. A suitable polar coordinate system is set up on the floor of the gallery with units in metres and radians. $R$ is modelled as being the region enclosed by two curves, $C _ { 1 }$ and $C _ { 2 }$. The polar equations of $C _ { 1 }$ and $C _ { 2 }$ are
$$\begin{array} { l l }
C _ { 1 } : r = 5 , & - \frac { 1 } { 2 } \pi \leqslant \theta \leqslant \frac { 1 } { 2 } \pi \\
C _ { 2 } : r = 3 \cosh \theta , & - \frac { 1 } { 2 } \pi \leqslant \theta \leqslant \frac { 1 } { 2 } \pi
\end{array}$$
Both curves are shown in the diagram, with $R$ indicated.\\
\includegraphics[max width=\textwidth, alt={}, center]{7b2bfb4e-524f-4d1c-ae98-075c7fb404f9-6_1481_821_836_251}
The gallery must buy tins of paint to paint $R$. Each tin of paint can cover an area of $0.5 \mathrm {~m} ^ { 2 }$.\\
Determine the smallest number of tins of paint that the gallery must buy in order to be able to paint $R$ completely.
\hfill \mbox{\textit{OCR Further Pure Core 2 2023 Q10 [7]}}