1MA0 Foundation June 2017 Paper 1 Q17
*17 ABC is an isosceles triangle.
Diagram NOT accurately drawn
\(AC = BC\)
ABD is a straight line.
Angle \(ACB = 70^\circ\)
Angle \(EBD = 80^\circ\)
Angle \(CBE = x^\circ\)
Work out the value of \(x\).
Give reasons for your answer. (4)
| Answer | Mark | Notes |
|---|---|---|
| 45 | 4 | M1 for complete method to find angle ABC e.g. \((180 - 70) \div 2\) (= 55) M1 for complete method to find \(x\) e.g. angle CBD = \(180 - \text{``}55\text{''}\) (= 125) and \(\text{``}125\text{''} - 80\) A1 cao C1 base angles of an isosceles triangle are equal and the sum of the angles in a triangle is 180 and the sum of the angles on a straight line is 180 or M1 for complete method to find angle BAC e.g. \((180 - 70) \div 2\) (= 55) M1 for complete method to find \(x\) e.g. \(70 + \text{``}55\text{''}\) (= 125) and \(\text{``}125\text{''} - 80\) A1 cao C1 base angles of an isosceles triangle are equal and the exterior angle of a triangle is equal to the sum of the two interior opposite angles |