1MA0 Foundation March 2013 Paper 1 Q18
*18
Diagram NOT accurately drawn
Triangle \(ABC\) is a right-angled triangle.
\(ADB\) is a straight line.
\(DA = DC\)
Angle \(BCD = 20^\circ\)
Work out the size of the angle marked \(x\).
You must give reasons for each stage of your working. (4)
| Answer | Mark | Notes |
|---|---|---|
| \(35^\circ\) with reasons | 4 | M1 for correct method to find one angle eg 70 or 110 (angles could be on the diagram) M1 for a complete correct method to work out \(x\) A1 (dep on M1) for \(35^\circ\) C1 for complete geometric reasons for their chosen method without extras eg exterior angle = sum of interior opposite angles and base angles of an isosceles triangle are equal OR angles in a triangle add up to 180 and angles on a straight line add up to 180 and base angles of an isosceles triangle are equal OR M1 \(x + x + 20 + 90 = 180\) M1 for a complete correct method to work out \(x\) A1 (dep on M1) for \(35^\circ\) C1 for complete geometric reasons for their chosen method without extras eg angles in a triangle add up to 180 and base angles of an isosceles triangle are equal |