# Circles

## Concept Lectures

Session 01 : Circles: Definition, centre, radius, interior and exterior of a circle.

Session 02 : Circles: Minor Arc, Major Arc, Central Angle.

Session 03 : Circles: Chord, diameter, segment, major segment, minor segment, secant and tangent.

Session 04 : Theorem: If two arcs of a circle (or of congruent circles) are congruent, then corresponding chords are equal.

Session 05 : Theorem: If two chords of a circle (or of congruent circles) are equal, then corresponding arcs are congruent.

Session 06 : Theorem: The perpendicular from the center of a circle to a chord bisects the chord.

Session 07 : Theorem: The line joining the center and the mid-point of a chord is perpendicular to the chord.

Session 08 : Demonstration: How many circles can pass through one, two, three and more number of points on a plane?

Session 09 : Demonstration: Centre of the Circle lies on the angle bisector of angle between two equal chords.

Session 10 : Theorem: Centre of the Circle lies on the angle bisector of angle between two equal chords.

Session 11 : Theorem: If the centre lies on angle bisector of the angle between two chords then the chords are equal.

Session 12 : Theorem: Line joining the centres of two intersecting circles perpendicularly bisects the common chord

## Problem Solving Sessions : Section 1

Session 13 : Problem # 01 : The radius of a circle is 13 cm and length of one of its chord is 10 cm. Find the distance of the chord from the center.

Session 14 : Problem # 02 The radius of the given circle is 5 cm. OR ⊥PQ, OC⊥AB and PQ || AB. Find the length of RC