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
- 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