Circle Properties 2

A circle is a plane figure bounded by one curved line, every point of which is equally distant from a certain point within, which is called its center.

Definitions related to circles:

Arc:  A continuous piece of a circle is called an arc. In other words, any portion of the circumference of a circle is called an arc.

Chord: A straight line joining any two points on the circumference of a circle is called a chord.

Circumference: The perimeter of a circle is called its circumference

Diameter:  Any straight line drawn through the centre and terminating at both ways by the circumference is called a diameter.

Origin:  Origin refers to the center of a circle

Pi (  ):  An approximate value of  is 22/7 which is correct to two decimal places. A more accurate value of  is 3.14159 which is correct to five decimal places.  

Radius: The constant distance of every point on the circle from its centre is called the radius of the circle. It is half of the diameter.

Sector:  A sector is that part of a circle, which lies between an arc and two radii joining the extremities of the centre. The most important sector is a quadrant, which is one-fourth of the circle.  

Tangent of a circle:  It is a line perpendicular to the radius that touches only one point on the circle.

Circumference of a circle: = 2 r where  is 22/7 or 3.14159

Area of a circle = r²

Length of a Circular Arc: (with central angle )

• if the angle  is in degrees, then length =  x (/180) x r
• if the angle  is in radians, then length = r x

Area of Circle Sector: (with central angle )

• if the angle is in degrees, then area = (/360) x  r²
• if the angle is in radians, then area = [(/(2)] x r²

If you feel you’re ready, try the circle test.