This document defines key terms related to circles and cylinders such as radius, diameter, circumference, chord, and sector. It provides the formulas for calculating the circumference of a full circle (C=πD or C=2πr) and the perimeter of a semicircle (P=(π×d)/2 + d) and includes examples of using the formulas to find the circumference given the diameter or radius of a circle.

1. CIRCLES AND CYLINDERS
YEAR 8 MATHEMATICS

3. Radius or Radii (plural) Sector Diameter
Circumference Arc Chord
Quadrant Segment Semi circle

4. Therefore the formula to remember for the
circumference of a circle is:
c = πd OR
c = 2πr

6. C=ΠD
Where D = 24cm and Π=3.14
Therefore
C = 24 x 3.14
C ≈ 75.39cm

7. C=2Πr
Where r = 5cm and Π=3.14
Therefore
C = 2 x 3.14 x 5
C ≈ 31.41 cm

8. Remember that the circumference of the circle calculates the
distance on the arc (around the outside) so if you are to find the
perimeter of the semi circle we need to include the diameter.
(π ×12)
P= +12
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