Foundation November 2024 Paper 2 Q13
13 \(ABC\) is a triangle.
\(BCD\) is a straight line.
Show that triangle \(ABC\) is isosceles.
Give a reason for each stage of your working. (4)
| Answer | Mark | Mark scheme |
|---|---|---|
| Shown | M1 | for a method leading to the evaluation of another angle, (\(BAC =\)) \(360 - 310\ (= 50)\) or (\(ACB =\)) \(180 - 115\ (= 65)\) |
| M1 | for a method to find at least 2 angles, eg (\(BAC =\)) \(360 - 310\ (= 50)\) and (\(ACB =\)) \(180 - 115\ (= 65)\) | |
| C2 | (dep M2) \(CBA = 65^\circ\) and statement and appropriate angle reasons, eg statement \(ACB = CBA\ (= 65^\circ)\) or two angles are equal (so it is isosceles) and angles at a point add up to 360, angles on a straight line add up to 180, angles in a triangle add up to 180, OR (dep M2) \(CBA = 65^\circ\) and statement and appropriate angle reasons, eg statement \(ACB = CBA\ (= 65^\circ)\) or two angles are equal (so it is isosceles) and the exterior angle of a triangle is equal to the sum of the interior opposite angles and angles on a straight line add up to 180 or angles in a triangle add up to 180 | |
| (C1 | (dep on M1) for any one appropriate reason related to method shown) |
Additional guidance
Angles may be seen on diagram
Underlined words need to be shown; reasons need to be linked to their method.