# What are the rules of circle geometry?

## What are the rules of circle geometry?

Circle theorems: where do they come from?

• The angle at the centre is twice the angle at the circumference.
• The angle in a semicircle is a right angle.
• Angles in the same segment are equal.
• Opposite angles in a cyclic quadrilateral sum to 180°

How many theorems are there in circle geometry?

This collection holds dynamic worksheets of all 8 circle theorems.

### What are the 8 circle theorems?

What are the 8 circle theorems?

• Circle Theorem 1 – Angle at the Centre.
• Circle Theorem 2 – Angles in a Semicircle.
• Circle Theorem 3 – Angles in the Same Segment.
• Circle Theorem 4 – Cyclic Quadrilateral.
• Circle Theorem 5 – Radius to a Tangent.
• Circle Theorem 6 – Tangents from a Point to a Circle.

What are the three parts of a circle?

Important Circle Parts

• Radius: The distance from the center of the circle to its outer rim.
• Chord: A line segment whose endpoints are on a circle.
• Diameter: A chord that passes through the center of the circle.
• Secant: A line that intersects a circle in two points.

#### What is a chord of circle?

In plane geometry, a chord is the line segment joining two points on a curve. The term is often used to describe a line segment whose ends lie on a circle. All angles inscribed in a circle and subtended by the same chord are equal.

What are the types of circle?

Types of Circles – Concentric circles, Contact of circles, Orthogonal circles. A circle is a closed shape simple figure in which all the points lying on the surface of the circle joining its centre are equal and known as radius of the circle. A huge collection of circles is called a family of circles.

## What do you need to know about circle geometry?

8.2 Circle geometry (EMBJ9) Terminology. The following terms are regularly used when referring to circles: Arc — a portion of the circumference of a circle. Chord — a straight line joining the ends of an arc. Circumference — the perimeter or boundary line of a circle.

Are there any obvious theorems in circle geometry?

The theorems of circle geometry are not intuitively obvious to the student, in fact most people are quite surprised by the results when they first see them. They clearly need to be proven carefully, and the cleverness of the methods of proof developed in earlier modules is clearly displayed in this module.

### When is an angle equal to a circle?

Circle theorems equal to any angle in the alternate segment A quadrilateral iscyclic(that is, the four vertices lie on a circle) if and only if the sum of each pair of opposite angles is two right angles

Which is the most elementary figure in geometry?

Lines and circles are the most elementary figures of geometry − a line is the locus of a point moving in a constant direction, and a circle is the locus of a point moving at a constant distance from some fixed point − and all our constructions are done by drawing lines with a straight edge and circles with compasses.