Higher June 2018 Paper 5 Q11
11 The diagram shows two right-angled triangles ABD and BCD, sharing a common side BD.
AD = 10 cm, BC = 12 cm and angle DBC = 60°.
Not to scale
Work out the length of AB. [6]
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| 8 nfww | 6 | nfww - must check method before giving 6 marks must not come from wrong working | |
| B1 for cos 60 = 0.5 oe soi M1 for \(\dfrac{\text{BD}}{12} = \cos 60\) oe A1 for [BD =] 6 AND M2 for \(\sqrt{10^2 - \textit{their}\text{ BD}^2}\) or M1 for their \(\text{BD}^2 + \text{AB}^2 = 10^2\) oe or for \(10^2 -\) their \(\text{BD}^2\) | e.g. sin 30 = 0.5 e.g. \(\dfrac{\text{BD}}{12} = \sin 30\) For M2 or M1 0 < their BD < 10 and BD must be identified first on diagram or in working | ||