Class 9 Maths Circles – Get here the Notes for Class 9 Circles. Candidates who are ambitious to qualify the Class 9 with good score can check this article for Notes. This is possible only when you have the best CBSE Class 9 Maths study material and a smart preparation plan. To assist you with that, we are here with notes. Hope these notes will helps you understand the important topics and remember the key points for exam point of view. Below we provided the Notes of Class 9 Maths for topic Circles

**Class:**9th**Subject:**Maths**Topic:**Circles**Resource:**Notes

## CBSE Notes Class 9 Maths Circles

Candidates who are pursuing in Class 9 are advised to revise the notes from this post. With the help of Notes, candidates can plan their Strategy for particular weaker section of the subject and study hard. So, go ahead and check the Important Notes for Class 9 Maths Circles from this article.

**CIRCLES AND ITS RELATED TERMS**

The collection of all the points in a plane, which are at a fixed distance from a fixed point in the plane, is called a circle.

A circle is a closed curve all of whose points lie in the same plane and are at the same distance from the centre.

The fixed point is called the centre of the circle and the fixed distance is called the radius of the circle.

**Note :** The line segment joining the centre and any point on the circle is also called a radius of the circle.

**INTERIOR AND EXTERIOR OF A CIRCLE**

A circle divides the plane on which it lies into three parts. They are (i) inside the circle, which is also called the interior of the circle. (ii) the circle and (iii) outside the circle, which is also called the exterior of the circle

**CHORD**

A chord of a circle is a line joining two points of the circumference. A chord passes through the centre is called diameter.

**Note :** Diameter is the longest chord and all diameters have the same length, which is equal to two times the radius.

A piece of a circle between two points is called an arc. In a circle equal chords have equal arcs.

When P and Q are ends of a diameter, then both arcs are equal and each is called a semicircle.

The length of the complete circle is called its circumference.

The region between a chord and either of its arcs is called segment of the circle.

The region between an arc and the two radii, joining the centre to the end points of the arc is called a sector

The minor arc corresponds to the minor sector and the major arc corresponds to the major sector.

When two arcs are equal, that is, each is a semicircle, then both segments and both sectors become the same and each is known as a semicircular region.

**Theorem 1:** Equal chords of a circle subtend equal angles at the centre.

**Theorem 2 :** If the angles subtended by the chords of a circle at the centre are equal, then the chords are equal.

**PERPENDICULAR FROM THE CENTRE TO A**

**CHORD**

**Theorem 3 :** The perpendicular from the centre of a circle to a chord bisects the chord.

**Theorem 4 :** The line drawn through the centre of a circle to bisect a chord is perpendicular to the chord.

**Theorem 5 :** There is one and only one circle passing through three given non-collinear points.

**Remark :** If ABC is a triangle, then by above given Theorem there is a unique circle passing through the three vertices A, B and C of the triangle. This circle is called the circumcircle of the AABC. Its centre and radius are called respectively the circumcentre and the circumradius of the triangle.

**EQUAL CHORDS AND THEIR DISTANCES FROM THE CENTRE**

**Theorem 6 :** Equal chords of a circle (or of congruent circles) are equidistant from the centre (or centres).

**Theorem 7 :** Chords equidistant from the centre of a circle are equal in length.

**ANGLE SUBTENDED BY AN ARC OF A CIRCLE**

**Result :** Congruent arcs (or equal arcs) of a circle subtend equal angles at the centre.

**Theorem 8 :** The angle subtended by an arc at the centre is double the angle subtended by it at any point on the remaining part of the circle.

**Note :** Theorem gives the relationship between the angles subtended by an are at the centre and at a point on the circle.

**ANGLE FORMED IN THE SEGMENT**

**Theorem 9:** Angles in the same segment of a circle are equal.

**Note :** Angle in a semicircle is a right angle.

**Theorem 10 :** If a line segment joining two points subtends equal angles at two other points lying on the same side of the line containing the line segment, the four points lie on a circle (i.e. they are concyclic).

**CYCLIC QUADRILATERAL:**

A quadrilateral ABCD is called cyclic if all the four vertices of it lie on a circle.

**Theorem 11:** The sum of either pair of opposite angles of a cyclic quadrilateral is 180°.

**Theorem 12 :** If the sum of a pair of opposite angles of a quadrilateral is 180°, the quadrilateral is cyclic.

### Class 9 Key Points, Important Questions & Practice Papers

Hope these notes helped you in your schools exam preparation. Candidates can also check out the Key Points, Important Questions & Practice Papers for various Subjects for Class 9 in both Hindi and English language form the link below.

Class 9 Maths | कक्षा 9 गणित |

Class 9 Science | कक्षा 9 सामाजिक विज्ञान |

Class 9 English | |

Class 9 Social Science |

### Class 9 NCERT Solutions

Candidates who are studying in Class 9 can also check Class 9 NCERT Solutions from here. This will help the candidates to know the solutions for all subjects covered in Class 9th. Candidates can click on the subject wise link to get the same. Class 9 Chapter-wise, detailed solutions to the questions of the NCERT textbooks are provided with the objective of helping students compare their answers with the sample answers.

### Class 9 Mock Test / Practice

Mock test are the practice test or you can say the blue print of the main exam. Before appearing in the main examination, candidates must try mock test as it helps the students learn from their mistakes. With the help of Class 9 Mock Test / Practice, candidates can also get an idea about the pattern and marking scheme of that examination. For the sake of the candidates we are providing Class 9 Mock Test / Practice links below.

### Class 9 Exemplar Questions

Exemplar Questions Class 9 is a very important resource for students preparing for the Examination. Here we have provided Exemplar Problems Solutions along with NCERT Exemplar Problems Class 9. Question from very important topics is covered by Exemplar Questions for Class 9.

CBSE Class 9 Maths Notes Science Notes Social Science Notes English Notes

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