Higher June 2017 Paper 1 Q18
18
\(ABCD\) is a rhombus.
The coordinates of \(A\) are \((5, 11)\)
The equation of the diagonal \(DB\) is \(y = \dfrac{1}{2}x + 6\)
Find an equation of the diagonal \(AC\). (4)
| Answer | Mark | Notes |
|---|---|---|
| \(y = -2x + 21\) | P1 | shows evidence of understanding that \(AC\) is perpendicular to \(DB\), or states the gradient of \(DB\) as 0.5 oe |
| P1 | shows a process to find the gradient of a perp. line e.g. use of \(-\dfrac{1}{m}\) or states \(y = -2x + c\) or states the gradient of \(AC\) as \(-2\) | |
| P1 | (dep on P2) for sub. of \(x = 5\), \(y = 11\) into \(y = mx + c\) where \(m\) is their found gradient for \(AC\). | |
| A1 | oe |