Chapter 10 Circles Ex 10.1
How many tangents can a circle have?
There can be infinitely many tangents to a circle.
Fill in the blanks:
(i) A tangent to a circle intersects it in ………… point(s).
(ii) A line intersecting a circle in two points is called a ………… .
(iii) A circle can have parallel tangents at the most ………… .
(iv) The common point of a tangent to a circle and the circle is called ……….. .
(iv) Point of contact.
A tangent PQ at a point P of a circle of radius 5 cm meets a line through the centre O at a point Q so that OQ = 12 cm. Length PQ is
(a) 12 cm
(b) 13 cm
(c) 8.5 cm
(d) 199−−−√ cm
Radius of the circle = 5 cm
OQ = 12 cm
∠OPQ = 90°
[The tangent to a circle is perpendicular to the radius through the point of contact]
PQ2 = OQ2 – OP2 [By Pythagoras theorem]
PQ2 = 122 – 52 = 144 – 25 = 199
PQ = 199−−−√ cm.
Hence correct option is (d).
Draw a circle and two lines parallel to a given line such that one is a tangent and the other, a secant to the circle.
A line m is parallel to the line n and a line l which is secant is parallel to the given line.