Circles

Circumference

Distance around the outside of a circle

Centre

Point in the middle that is an distance from all parts on the circumference

Diameter

Straight line passing through the centre of a circle that touches its circumference at both ends.

Radius

A line from the center of a circle to its circumference.

Arc

Part of the circumference.

Chord

Straight line between two points on the circumference.

Sector

Area enclosed by an arc and two radii.

Quadrant

Area enclosed by an arc and two radii at right angles.

Segment

Area enclosed by an arc and a chord.

Semi-circle

Area enclosed by an arc and the diameter

Tangent

Straight line that touches the circumference at one point only.

Normal

Straight line that is perpendicular to a tangent: point of intersection between the two is called the point of contact

What is this?

Constructing tangents from a given point outside a circle

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Constructing an external tangent between two circles

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Constructing an internal tangent between two circles

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Constructing two circles in contact externally

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Constructing two circles in contact internally

What is this?

Constructing an external tangent arc between two circles

What is this?

Constructing an internal tangent arc between two circles