NCERT Book Class 9 Maths Circles Questions

(A) Main Concepts and Results

Circle, radius, diameter, chord, segment, cyclic quadrilateral.

• Equal chords of a circle (or of congruent circles) subtend equal angles at the centre,

• If the angles subtended by the chords of a circle (or of congruent circles) at the centre (or centres) are equal, then the chords are equal,

• The perpendicular drawn from the centre of the circle to a chord bisects the chord,

• The line drawn through the centre of a circle bisecting a chord is perpendicular to the chord,

• There is one and only one circle passing through three given non-collinear points,

• Equal chords of a circle (or of congruent circles) are equidistant from the centre (or centres),

• Chords equidistant from the centre of a circle are equal in length,

• If two chords of a circle are equal, then their corresponding arcs are congruent and conversely, if two arcs are congruent, then their corresponding chords are
equal,

• Congruent arcs of a circle subtend equal angles at the centre,

• The angle subtended by an arc at the centre is double the angle subtended by it at any point on the remaining part of the circle,

• Angles in the same segment of a circle are equal,

• If a line segment joining two points subtends equal angles at two other points lying on the same side of the line containing the line segment, then the four points are concyclic,

Please refer to attached file for NCERT Class 9 Maths Circles Questions