# GCSE Circle Theorems

GCSE circle theorems; good detailed revision notes with a couple of exam style questions at the end.

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## Other slides in this set

### Slide 2

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90°
Angles in a Semi-circle 90°
Angles in semicircle = 90 degrees.
OR
Angles subtended by a diameter = 90

### Slide 3

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Angles in the Same Sector
These angles same
These angles same size!
size!
Angles in the same segment are equal.…read more

### Slide 4

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A+C=180
B+D=180
Opposite angles in a Cyclic
Quadrilateral (four-sided shape with its B
corners touching the edge of a circle)
A
C

### Slide 5

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Centre Angle/Circumference Angle
A Angle A is half of angle B.
The angle at the
circumference is half of the
angle at the centre.
OR
B The angle at the centre is
double the angle at the
circumference.

### Slide 6

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Alternate Segment Rule
This applies where
Angle A = Angle B
there is a triangle in a
Angle C = Angle D circle and one corner
A is touching a tangent
to the circle.
C
Angles in alternate
segments are
equal.