IGCSE›Cambridge IGCSE Maths›Mind mapsCircles, Arcs & SectorsCambridge IGCSE Maths: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsCircle basicsCircumference: C=2πrC = 2\pi rC=2πr or C=πdC = \pi dC=πdArea: A=πr2A = \pi r^2A=πr2Diameter = 2 × radiusBoth formulas are given in the examArc lengthAn arc is part of the circumferenceθ360×2πr\frac{\theta}{360} \times 2\pi r360θ×2πrMinor arc is shorter, major arc is longerSector areaA sector is a pie-slice of a circleθ360×πr2\frac{\theta}{360} \times \pi r^2360θ×πr2Extended: major sectors over 180°Circles & sectorsarcs and sectorsπrdWorked exampleRadius 6 cm, sector angle 60°Arc = 60360×2π(6)\frac{60}{360} \times 2\pi(6)36060×2π(6)Answer: 2π≈2\pi \approx2π≈ 6.28 cmIn terms of πLeave π as a symbol, e.g. 12π12\pi12π cmOtherwise use calculator π, round to 3 s.f.Compound shapes: treat circular and straight parts separatelyExam tipsUsing diameter as radius makes area 4× too bigCore sector angles are factors of 360°A decimal when 'in terms of π' loses the accuracy mark