Circle Theory
2x
x
This is the ARC
o
Centre of Circle
The Angle x subtended at the centre of a circle by an arc is twice the size of the angle on the circumference subtended by the same arc.
2x
x
o
This is the ARC
Centre of Circle
Angle subtended at the Centre is twice the angle at the circumference
x
x
x
We are ALL EQUAL
This is the Arc
Minor Segment
Major Segment
o
A
B
CDx
180-x
If this angle was 600 then angle BCD would be 1800-600=1200
1200
Points which lie on the circumference of the same circle are called cyclic (or concyclic)points. A cyclic quadrilateral is a quadrilateralwith all its four corners (vertices) on thecircumference of the same circle.
T
A
B
O
TA=TB
Tangent
Tangent
Major Segment
Minor SegmentA B C
E
D
The Shaded Segment BED is called the alternate segment to the angle CBDThe angle between a tangent to a circle and a chord drawn through the pointof contact is equal to any angle subtended by the chord at the circumference in the alternate segment
Center of Circle
Diameter
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