What is the circumference?

The perimeter

What is the diameter?

A line going through the centre of the circle

What is the radius?

Half the diameter

What is a chord?

A line which both ends connect to the circumference

What is a tangent?

A line that touches the circle at one point from the outside

What is a sector?

What is an arc?

What are segments?

Areas split by a chord

Which rule is this?

The angle in a semi circle is a right angle.

two radii form a triangle

Which rule is this?

A tangent meets a radius at 90

Which rule is this?

A triangle formed by two radii are isosceles.

All radii are the same length.

What rule is this?

A diameter bisects a chord at a right angle.

Which rule is this?

The angle at the centre is twice the angle at the circumference.

What rule is this?

Angles in the same segment are equal

All triangles drawn from a chord will have the same angle where they touch the circumference

Which rule is this?

Opposite angles in a cyclic quadrilateral = 180^{o}

Which rule is this?

Tangents from the same point are the same length.

also form 2 congruent right angle triangles

Which rule is this?

Alternate segment theorem

angle in the alternate segment are equal

Which rule is this?

Internal intersection

AE x CE = DE x BE

measured from intersection

Which rule is this?

External intersection

MP x MQ = MN x MO

Measured from intersection.