June 2024 Paper 1 Q12
12 In triangle \(ABC\), \(\quad \cos A = \dfrac{3}{4}\)
Work out the length \(BC\). [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| \(12^2 + 10^2 - 2 \times 12 \times 10 \times \dfrac{3}{4}\) | M1 | oe in a fully correct substitution could already be under \(\sqrt{\phantom{x}}\) |
| \(144 + 100 - 180\) or 64 | M1dep | |
| 8 | A1 | \(\pm 8\) is A0 |
Additional guidance
| \(\cos\dfrac{3}{4}\) used in the working will not score unless recovered into a fully correct calculation that scores to at least the first M mark |