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Basic Terminology
Basic Terminology
- Circle: a round plane figure whose boundary (circumference) consists of points equidistant (radius) from a fixed point called the centre (labelled O)
- Radius: straight line segment from the centre to the circumference of a circle (e.g. OA, OB, OC)
- Diameter: straight line segment that passes through the centre of the circle, endpoints lie on the circle (e.g. BC)
Circle Features
Circle Features
- Chord: an interval joining two points on the circle (e.g. CD, FG)
- Arc: part of the circumference of a circle (e.g. arc CD, arc AE)
- Segment: area within a circle enclosed between an arc and a chord (e.g. blue area enclosed by chord and arc CD)
- Sector: area within a circle enclosed by two radii of a circle and the arc between them (e.g. red area enclosed by radii OA and OE)
- Tangent: straight line that touches the circle at only one point (point of contact) (e.g. dotted line with point of contact E)
- External point: point lying outside (exterior) of circle (e.g. point B)
- Secant: straight line that intersects with circle at two points (e.g. BC)
Other Terminology
Other Terminology
- Concentric Circles: circles that share the same centre, the larger circle often surrounding the smaller
- Intersecting Circles: circles that cross one another at one or two points
- Cyclic Quadrilateral: quadrilateral formed from 4 vertices that lie on a common circle (e.g. blue quadrilateral HIJK)
- Collinear: three points that lie on a straight line (e.g. E, F & G)
- Intercepts: line segment whose endpoints are the intersection of two lines (e.g. LP, MP, NP, OP)
New Terminology
New Terminology
- Angle at the centre: angle formed by joining the ends of an arc or chord to the centre of a circle (e.g. angle AOB)
- Angle at the circumference: angle formed by joining the ends of an arc or chord to another point on the circumference (e.g. angle ACB, angle ADB)
- Angle standing on the same arc: two points A and B divide a circle into two arcs, the larger one being the major arc and the smaller one the minor arc
- When the ends of an arc or chord are joined to two different points in the same segment the angles are said to be standing on the same arc (e.g. angles ADB & ACB)
- Subtend: ends of an interval joined to a point, the angle formed is said to be subtended by the interval (e.g. angle AOB subtended by interval AB to O)
Definitions adapted from Google, Wikipedia, Signpost Mathematics 10 Advanced (2nd ed), Maths in Focus, AMSI (Australian Mathematical Sciences Institute), & the Penguin Dictionary of Mathematics
Images created in GeoGebra Geometry
Relevant Vocabulary
Relevant Vocabulary
Stage 4 & 5
Stage 4 & 5
Algebraic Techniques: [S4 Algebraic Techniques 1]
Equations: [S4 Equations]
Ratios: [S4 Ratios and Rates]
Length: [S4 Length]
Angle Relationships: [S4 Angle Relationships]
Right-Angled Triangles (Pythagoras & Trigonometry):
Properties of Geometrical Figures:
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