June 2022 Paper 2 Q4
4 The diagram shows a triangle \(ABC\).
\(AB\) is the shortest side.
The lengths of \(AC\) and \(BC\) are 6.1 cm and 8.7 cm respectively.
The size of angle \(ABC\) is 38°
Find the size of the largest angle.
Give your answer to the nearest degree. [3 marks]
| Scheme | Marks | AO |
|---|---|---|
| Uses the sine rule Or Substitutes correctly into the cosine rule | M1 | 1.1a |
| Obtains a value of 61 or 61.410964… rounded or truncated Condone answer (in radians) of 1.0718… or 0.4364… PI by correct obtuse angle or 81 Or Obtains correct length \(AB\) = 3.9367… Or \(AB^2\) = 15.4998… | A1 | 1.1b |
| Deduces the largest angle is 119 AWRT CAO | A1 | 2.2a |
| (3 marks) |