A2 June 2019 Paper 1 Q2
2 The plane \(x + 2y + cz = 4\) is perpendicular to the plane \(2x - cy + 6z = 9\), where \(c\) is a constant. Find the value of \(c\). [3]
| Scheme | Marks | AO |
|---|---|---|
| \((\mathbf{i} + 2\mathbf{j} + c\mathbf{k}).(2\mathbf{i} - c\mathbf{j} + 6\mathbf{k}) = 0\) | M1 | 1.1a |
| \(\Rightarrow 2 - 2c + 6c = 0\) | A1 | 1.1b |
| \(\Rightarrow c = -\frac{1}{2}\) | A1 | 1.1b |
| [3] |
Notes
M1: scalar product = 0