Page 1 - Lesson Notes-Introduction Ch-10 (Circles)

SAI International School
Class X

Mathematics – Lesson Notes

Chapter-10: Circles

Sub Topics – Introduction, Tangents, Theorem 10.1

Important terms-

 Circle- A figure made by all the points which are at the same distance from a
fixed point is called a Circle.
 Centre- The fixed point is known as the centre of the circle.
 Radius- The distance from any point on the circle to the fixed point is the
radius. Any line segment which joins the centre and any point on the circle is
known as the Radius.
 Chord- Any line segment made by joining any two points on the boundary of
the circle is called Chord.
 Diameter- Diameter is two times the radius. It is the longest chord on the
circle which passes through the centre. All the diameters have the same
length.
 Circumference- The length of the boundary of the circle is called the
circumference of the circle.

 Arc- An arc is the part of the circle joining two points on the circumference of
the circle.
 Sector- An area made by an arc and two radii of the circle, by joining the
centre to the endpoints of the arc is called Sector.

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