Why are circles different to other 2D shapes?
Circles just have their own language!
The circumference of a circle is its perimeter.
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 ” – 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.
Other than that, working with circle formulas is just like working with any other formula:
- WRITE DOWN – what you know
– what you want to know
- Pick correct FORMULA
- SUBSTITUTE and SOLVE
Edexcel GCSE Maths Notes
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