Circle Theorems and Properties

A hypothesis that needs testing

A mathematical guess

A statement that has been proven to be true every time

A statement that is sometimes true

The radius of the circle

The line connecting two points on the circle

The distance around the edge of the circle

The area inside the circle

A line that touches the circle at one point

A line segment connecting two points on the circle

The longest line in the circle

A line from the center to the circumference

An angle formed by a tangent

An angle formed at the edge of the circle by two lines from the arc

An angle formed at the center of the circle

An angle formed by a diameter

180°

90°

360°

270°

They are complementary

They sum to 180°

They are equal

They are always different

45°

120°

60°

90°

A quadrilateral with all sides equal

A quadrilateral with all angles equal

A quadrilateral with all corners on the circle

A quadrilateral with one angle 90°

The angle at the center is three times the angle at the circumference

The angles are equal

The angle at the center is twice the angle at the circumference

The angle at the center is half the angle at the circumference

The angle between a chord and a tangent is equal to the angle subtended by the diameter

The angle between a chord and a tangent is equal to the angle at the center

The angle between a chord and a tangent is always 90°

The angle between a chord and a tangent is equal to the angle in the opposite segment