| Exam Board | OCR MEI |
|---|---|
| Module | Paper 3 (Paper 3) |
| Year | 2018 |
| Session | June |
| Marks | 3 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Sine and Cosine Rules |
| Type | Basic cosine rule application |
| Difficulty | Easy -1.2 This is a straightforward single-step application of the cosine rule to find one missing side, then add three sides for perimeter. The diagram provides two sides and the included angle, making this a routine textbook exercise requiring only direct formula substitution with no problem-solving or multi-step reasoning. |
| Spec | 2.02a Interpret single variable data: tables and diagrams |
| Answer | Marks | Guidance |
|---|---|---|
| \([BC^2] = 32^2 + 14^2 - 2 \times 32 \times 14\cos85°\) | M1 (3.1a) | Use of cosine rule to find BC; 1141.9… |
| \([BC] = 33.8\) cm | A1 (1.1) | 33.79… |
| Perimeter \(= 79.8\) cm | A1 (1.1) | Accept 80 provided 3 or more sf seen as BC |
**Question 1:**
$[BC^2] = 32^2 + 14^2 - 2 \times 32 \times 14\cos85°$ | M1 (3.1a) | Use of cosine rule to find BC; 1141.9…
$[BC] = 33.8$ cm | A1 (1.1) | 33.79…
Perimeter $= 79.8$ cm | A1 (1.1) | Accept 80 provided 3 or more sf seen as BC
---1 Triangle ABC is shown in Fig. 1.
\begin{figure}[h]
\begin{center}
\includegraphics[alt={},max width=\textwidth]{31bc8bde-8d37-4e97-94e2-e3e73aab55e9-4_451_565_520_744}
\captionsetup{labelformat=empty}
\caption{Fig. 1}
\end{center}
\end{figure}
Find the perimeter of triangle ABC .
\hfill \mbox{\textit{OCR MEI Paper 3 2018 Q1 [3]}}