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Home / Geometry / What is Circle, Radius, Diameter, Circumference, Centre ?

What is Circle, Radius, Diameter, Circumference, Centre ?

Definition of Circle: The set of all points in one plane that in a fixed distance from a center.
Definition of Center: Center of a Circle is a point inside the circle and is at an equal distance from all of the points on its circumference.

Example of centre:

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O is a centre of above circle.

Radius, Diameter, Circumference:      

Radius: The radius is the distance from the center to the edge.

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Diameter: The diameter starts at one side of the circle, passes through the center ends on other side.

or, if that line passes through the center it is called a Diameter.

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Circumference: The circumference is the distance around the edge of the circle.

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Here ABC is the circumference of the circle.

Chord: A line that goes from one point to another on the circle’s circumference is called a Chord.

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Here AC is chord of that circle.

Arc: An a part of the circumference is called an Arc.

***Some important information***

*** A straight line cannot intersect a circle in more than two points.

*** Chords equidistant from the centre of a circle are equal.

*** The diameter is the greatest chord of a circle.

*** Equal chords of a circle are equidistant from the centre.

*** The angle subtended by the same arc at the centre is double of the angle subtended by it at any point on the remaining part of the circle.

*** Angles in a circle standing on the same arc are equal.

*** The angle in the semi- circle is a right angle.

*** The sum of the two opposite angles of a quadrilateral inscribed in a circle is two right angles.

*** A parallelogram inscribed in a circle is a rectangle.

*** If two opposite angles of a quadrilateral are supplementary, the four vertices of the quadrilateral are con-cyclic.

*** In same circle radius are equal.

***Add between centre and arc is called radius.

***Some M.C.Q question***

1.Look at the circle below. The line segment appears to be

Screenshot_39

a.an arc     b. a perimeter   c. a radius   d. a diameter

2. Line segment AB is what part of this circle?

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a.circumference     b. radius       c. diameter

3. Is the shape flat or solid?

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a.flat         b. solid

4. Write the name of the following using the circle below:

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Name of the circle : —————

 

Diameter :———————-

 

Radius;————————-

 

Chord:————————-

5. What is this measurement called?

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a. Area     b. Circumference           c. Diameter             d. Radius

6.  (a) What type of angle is CAB?

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a. Acute             b. obtuse       c. right           d. straight

(b) What type of angle AOB?

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7. In circle O, which is the chord?

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a. AB               b. OD                 c. AC                   d.AO

 

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