NCERT Book Class 10 Maths Chapter 10 Circles

144 MATHEMATICS

CIRCLES 10
10.1 Introduction
You have studied in Class IX that a circle is a collection of all points in a plane
which are at a constant distance (radius) from a fixed point (centre). You have
also studied various terms related to a circle like chord, segment, sector, arc etc.
Let us now examine the different situations that can arise when a circle and a line
are given in a plane.
So, let us consider a circle and a line PQ. There can be three possibilities given
in Fig. 10.1 below:

Fig. 10.1
In Fig. 10.1 (i), the line PQ and the circle have no common point. In this case,
PQ is called a non-intersecting line with respect to the circle. In Fig. 10.1 (ii), there
are two common points A and B that the line PQ and the circle have. In this case, we
call the line PQ a secant of the circle. In Fig. 10.1 (iii), there is only one point A which
is common to the line PQ and the circle. In this case, the line is called a tangent to the
circle.