Edexcel IGCSE Maths

Revision Notes

4.12.1 Circles - Area & Circumference

Why are circles different to other 2D shapes?

  • Circles just have their own language!
  • The circumference of a circle is its perimeter
  • π is the number (3.14159 …) that links a circle’s diameter to its circumference
  • Diameter (d) is twice the radius (r)
    • You may be asked to give an area answer to a certain number of decimal places or significant figures
    • Alternatively you may be asked to give the exact value – or “give your answer in terms of π” – so this topic could crop up on the non-calculator paper!

Working with circles

  • You must know the formulas for the area and circumference of a circle
  • There are two versions for the circumference and it is important not to get the radius and diameter confused
  • Remember that d = 2r
    But you may prefer to remember the formulas by having different letters involved

Circumference-Formulae, IGCSE & GCSE Maths revision notes

  • Other than that, working with circle formulas is just like working with any other formula:
  1. WRITE DOWN – what you know (what you want to know)
  2. Pick correct FORMULA
  3. SUBSTITUTE and SOLVE

Worked Example

Circles - Area & Circumference Worked Example 1, downloadable IGCSE & GCSE Maths revision notes

Circles - Area & Circumference Worked Example 2, downloadable IGCSE & GCSE Maths revision notes

Semicircle-d=16, IGCSE & GCSE Maths revision notes

Circles - Area & Circumference Worked Example 3, downloadable IGCSE & GCSE Maths revision notes

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