A circle is a 2-Dimensional shape that can be drawn on a plane surface. A circle is made up of points on a given plane that is at an equal distance from a fixed point called Centre.
A, B, C and D are points lying on the circle. O represent the center of the circle. The distance between O and any point on the circle is called the radius of the circle.
OA = OB = OD = OC = Radius of circle
DB = AC = Diameter of circle
The diameter is double the radius of the circle. Diameter is any line passing through the Centre of the circle and whose endpoints lie on the circle. The circumference is the distance around the circle. We can call it the perimeter of a circle. A diameter divides the circles into two equal parts called semicircle.
Arc is a curved line that is part of the circumference. AB, BC are arcs. Part of a circle enclosed by two radii of a circle is called a sector. The most important sector is a quadrant. A quadrant is one-fourth of a circle.
A chord is a line segment that joins two points on the circle. AB is a chord that joins two points on a circle A and B. BD which is the diameter of the circle is the longest chord of the circle. Every chord divides a circle into two parts called segments. The smaller is called the minor segment and the larger one is called the major segment.
Perimeter and Area
R = Radius, D = Diameter, C = Circumference
If R is the radius, then the diameter of the circle is 2 X R.
The perimeter of a circle is called its circumference. The circumference can be calculated using formula 2 X π X R, where π = 3.14
The area of a circle can be calculated using formula A = π X R2 where π = 3.14
A central angle is an angle whose vertex is the center of the circle and whose sides are the radii of the circle. A full circle makes an angle of 360° at the center. A circle can be divided into smaller portions called arcs. Arcs are divided into minor arcs (central angle < 180°), major arcs (central angle is between 180° and 360°) and semicircles (central angle = 180°).
A secant is a line that intersects a circle in exactly two points. A tangent line intersects a circle in exactly one point and the point where the intersection occurs is called the point of tangency.
