The diagram shows two circles each with centre O. A, B, C and D are points on the circumference of the large circle. E, F and G are points on the circumference of the small circle. CGD and CFB are tangents to the small circle. Lines AEOC and FG intersect at 90° at X. GÔX = y°. [Figure with two circles, points, lines, angles]
- (a)(i)Find each of these angles, as simply as possible, in terms of y. Give reasons for your answers. GÊO[2]
- (a)(ii)GĈX[2]
- (a)(iii)DÂB[2]
- (b)Complete the sentence. Triangle EGC is congruent to triangle ....................[1]
- (c)Prove that triangle ADC is similar to triangle OGC. Give a reason for each statement you make.[2]
- (d)What special type of quadrilateral is AOGD?[1]
- (e)(i)Find the ratio area of triangle OGC : area of triangle ADC,[1]
- (e)(ii)Find the ratio area of triangle OGC : area of quadrilateral ABCD.[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.
- [2] (a)(i) y oe
- angle at centre = twice angle at circumference oe
- B1 for y/2
- [2] (a)(ii) 90 - y oe
- [2FT] (a)(iii) 2y oe
- or 2(90 – their (a)(ii))
- or 180-2 their (a)(ii))
- Angle in semicircle = 90°
- FT dependent on expressions in y
- B1 for 2y
- [1] (b) EFC
- [2] (c) Any two of
- • ∠OCG is common oe
- • ∠ADC = ∠OGC [= 90°]
- • ∠DAC = ∠GOC [= y]
- with no incorrect reason or fact stated
- B1 for one pair of angles
- [1] (d) Trapezium
- [1] (e)(i) 1 : 4 oe
- [1] (e)(ii) 1 : 8 oe
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