In this question, all lengths are in metres and all angles are in radians. The diagram shows a circle with centre O and radius 5. The points A, B, C and D lie on the circumference of the circle. Angle DOC = θ. Angle AOD = angle COB = 0.5. The length of the minor arc DC is 3.75. [Figure 6.1]
- (a)Show that θ = 0.75.[1]
- (b)Find the perimeter of the shaded region.[5]
- (c)Find the area of the shaded region.[3]
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Mark scheme
Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.
- [B1] 5θ=3.75 so θ = 0.75 AG Allow θ = 3.75/5 as a starting point
- [M1] For attempt to find the length of at least one chord. May be implied by a correct length.
- [A1] AB = 7.67(5) soi
- [A1] DC = 3.66(3) soi
- [B1] Arc length AD or BC : 5 × 0.5 soi oe Allow unsimplified
- [A1] 16.3
- [M2] (1/2 × 5² (1.75-sin1.75)) - (1/2 × 5² (0.75-sin 0.75))
- [A1] 8.7
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