Higher June 2019 Unit 2 Q18
18. Triangle \(ABC\) has sides \(AB\) = 17 cm, \(AC\) = 13 cm and \(BC\) = 23 cm, as shown below.
Diagram not drawn to scale
Calculate the size of \(C\hat{A}B\). [3]
| Scheme | Marks | Comments |
|---|---|---|
| (cos CAB =) (132 + 172 – 232) / (2×13×17) (=-71/442 OR -0.16(06…) ) | M2 | M1 for 232 = 132 + 172 – 2×13×17×cos CAB |
| (CAB =) 99(.2…°) | A1 | SC1 for the correct evaluation of either of the two other angles. ABC = 33(.9...) and ACB = 46(.8...). |