UNIQUE FRIENDS SCHOOLSA circle is a simple closed shape in geometry. A circle is the set of all points on a plane that are at the same distance from a fixed point called the centre.
A circle is a plane figure bounded by a curved line, called the circumference and every point on the line is equidistant from a fixed point called the centre of the circle.
The sum of angle at a point is 360°. The easiest way to construct a circle is by using a pair of compass. This is achieved by setting the compass to a given radius of a circle. Then placing the needle point of the compass at any point of choice to be the circle centre.
PARTS OF A CIRCLE
1 Centre: This is the fixed point in the middle of the circle. This is the mid point of a circle or diameter.
2 Radius: This is the distance from the centre to any point on the circle. Radius is half of a diameter.
3 Diameter: This is the straight line passing through the centre and touching two points on the circle. It is twice the radius.
4 Circumference: This is the boundary or the distance around the circle. A circumference of a curved line that bounds a circle.
5 Chord: This is a straight line joining two points on the circle. It divides the circle into two non-equal parts. It does not pass through the centre of the circle.
6 Arc: This is a curved part of the circumference.
7 Segment: This is the area of a circle bounded by chord and an arc.
8 Sector: This is the part of a circle that is bounded by two radii and an arc.
9 Quadrant: This is the lady of a circle bounded by two radii at an angle 90° to each other and an arc. The quadrants of a circle is ¼ of the circle; so, a circle had four quadrants.
10 Tangent: This is a straight line that touches the circumference at a point. It is always at the right angle to the radius.
Formula of a circle
Circumference of a circle
C= 2Ar
Area of a circle
A= IIr2
Where r= radius and A= 3.142
Examples of circular objects
Coins
Plates
Clocks
Wheels etc