NCERT Revision Notes for Chapter 10 Circles Class 10 Maths

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• Circle: A circle is a locus of a point which moves in such a way that the distance from that point is always fixed.

• Radius: The constant distance from the centre to the circumference of the circle.

• Secant: A line which intersect the circle at two different points.

• Chord: Any line segment joining the two points on the circumference of the circle.

• Diameter: The longest distance between the two points on the circumference of the circle. It is the longest chord.

Here, AO is the radius of the circle and AB is the diameter of the circle.

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 Tangent: A line which touches the circle exactly at one point.

The tangent at any point on a circle is perpendicular to the radius through the

point of contact.

In the above diagram l is tangent to the circle at point P. O is center, Then OP is perpendicular to l. 

OP ⊥ l. 

Tangent drawn from an external point to a circle

Length of the tangent: The length of the segment of the tangent from an external point P to the point of contact with the circle is called the length of the tangent from the point P to the circle.

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