Circle Theorems

1. An angle subtended at the centre, is twice the angle subtended at edge

2. The angle at the edge of semi circle, subtended by the diameter, is always a right angle

3. Opposite angles in a quadrilateral, where all its corners are on the edge of a circle, sum to 180o So in the below example Do = 78o and Co = 63o

4. Angles subtended on the same arc are equal

You will need to remember these theorems and be able to recognise them in order to solve problems.

Nothing in this section yet. Why not help us get started?

## Related Topics

Requires a knowledge of…

After this move on to…

## Related Questions

• 1
Vote
4

### What is a coordinate grid?

By Ryan McGuire on the 10th of January, 2013

• 2
5

### How do I figure out an angle?

By Ryan McGuire on the 10th of January, 2013

• 1
Vote
3

### What is the general form for a quadratic equation?

By Filsan on the 10th of January, 2013

• 1
Vote
2

### What does the graph of Y = x Linear look like?

By Filsan on the 10th of January, 2013

• 1
Vote
3

### What is the equation of a straight line graph?

By Filsan on the 10th of January, 2013

• 0
4

### How do I find 15% of a value?

By Verity Painter on the 8th of January, 2013

• 1
Vote
2

### What is an index law?

By Filsan on the 6th of December, 2012

• 0
1