There are two types of people who will tell you that you cannot make a difference in this world: those who are afraid to try and those who are afraid you will succeed. – **Ray Goforth**

# Lecture - 3 Chapter 10 Circles

00:00:05 NCERT Exercise 10.2 Question 7 Two concentric circles are of radii 5 cm and 3 cm. Find the length of the chord of the larger circle which touches the smaller circle.

00:09:32 NCERT Exercise 10.2 Question 8 A quadrilateral ABCD is drawn to circumscribe a circle (see Fig. 10.12). Prove that AB + CD = AD + BC

00:18:02 NCERT Exercise 10.2 Question 11 Prove that the parallelogram circumscribing a circle is a rhombus.

00:28:52 NCERT Exercise 10.2 Question 9 In Fig. 10.13, XY and X′Y′ are two parallel tangents to a circle with centre O and another tangent AB with point of contact C intersecting XY at A and X′Y′ at B. Prove that ∠ AOB = 90°.

00:39:12 NCERT Exercise 10.2 Question 10 Prove that the angle between the two tangents drawn from an external point to a circle is supplementary to the angle subtended by the line-segment joining the points of contact at the centre.

00:45:22 NCERT Exercise 10.2 Question 13 Prove that opposite sides of a quadrilateral circumscribing a circle subtend supplementary angles at the centre of the circle.