# Circle Theorem: Chord of a Circle, Theorem 1, Theorem 2, Theorem 3, Theorem 4, Theorem 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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## Circle

### Circle Theorem

• A circle can be defined as the locus of all points in a plane being at equidistant from a fixed point.
• The fixed point is the centre and whereas radius is the constant distance between any point on the circle and its centre.
• Circumference is the perimeter of a circle.
• Tangent of a circle is perpendicular to the radius at any point on it.
• Circle theorem includes:
• Concept of tangents
• Sectors
• Angles
• The chord of a circle and proofs

### Chord of a Circle

• The chord of a circle is the line segment joining any two points along the circumference of the circle.
• The largest chord passing through centre of the circle is its diameter.

### Circle Theorems and Proofs

(1) In a circle two equal chords subtend equal angles at the centre of the circle.

Proof:

In the above figure it՚s given in and

From equation (i) and (ii) , we get by (SSS rule) of congruency

we get

(2) The perpendicular to a chord bisects the chord if drawn from the centre of the circle.

Proof:

In the above figure , therefore

Also, it is given that in and .

From Equation (i) , (ii) and (iii) we get,

by R. H. S Axiom of congruency

Hence, by

(3) Equal chords of a circle are equidistant (equal distance) from the centre of the circle.

Proof:

and are joined by construction

It՚s given that in and

(Perpendicular to a chord bisects it)

(Perpendicular to a chord bisects it)

(Given)

From Equation (i) and (ii) ,