Unit Circle - Part 1
Unit Circle - Part 1


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The round shape figure is called Circles.

Example:Pizza,CD's,coins etc.

A Circle is the path of all the points that are equidistant from a fixed point on a given surface.

Part Description Example Properties
Center A point in a plane from which all points on the circle are equidistant
O is the center
A circle can have only one center
Radius A line segment with one end point at the center and other end point
on the circle

OP is a radius
The radius is always half the diameter R = d/2. A circle can have an infinite radii.
(plural of radius)
Diameter A chord that passes through the center of a circle.
AB is a diameter.
A diameter is twice the radius
d = 2r. It is always passes through the center. It is the
longest chord of a circle.
The length of a boundary of a circle.
O is the center
Every point on the circumference is equidistant from the center.
Chord A line segment whose end points are on the circle.
PQ is a chord.
A chord can be of any length.It may or may not pass through the center. Diameter is the longest chord.
Arc A part of a circle between any two points on the circle.
PQR is an arc.
It can be of any length. The
bigger arc is called major arc
and the smaller arc is called
minor arc.
Segment A chord divides a circle into two parts called segments.
PQR is an arc.
PQR is a minor segment .
RSP is the major segment.
Sector The region enclosed by two radii and an arc.
sector AOB
The smaller sector is called
minor sector and the bigger
sector is called major sector.
Semicircle Half circle. Diameter of a circle divides it into two semicircles.


Parts of -Circle
Arc and Chords
Equal Chords
Arc and Angles
Cyclic Quadrilaterals
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