Class 10 Maths Chapter 10 Revision Notes – Circles

Revising the Circles chapter in Class 10 Maths? These notes cover every theorem and result from Chapter 10 in one quick-reference page.

Last Updated: August 16, 2026

Class 10 Maths Chapter 10 – Revision Notes: Circles

• Tangent: a line that touches a circle at exactly one point (the point of contact); a secant touches it at two points.
• Core theorem 1: the tangent to a circle is perpendicular to the radius at the point of contact.
• Core theorem 2: the lengths of the two tangents drawn from an external point to a circle are equal.
• Tangent-length formula: for a point at distance d from the centre of a circle of radius r, tangent length = √(d²-r²).
• Key results built on the equal-tangent theorem: a parallelogram circumscribing a circle is a rhombus; for a quadrilateral circumscribing a circle, sum of opposite sides are equal (AB+CD=AD+BC).
• Angle result: the angle between two tangents from an external point (∠PTQ) and the angle subtended by the chord of contact at the centre (∠POQ) are supplementary; also ∠PTQ = 2∠OPQ.
• Construction skill: know how to draw a tangent and a secant parallel to a given line.
• Syllabus note (2026-27): 2 exercises — 10.1 (4 questions) and 10.2 (13 questions), 17 questions total.

Related

• Solutions
• Extra Questions (HOTS)
• Revision Notes
• Class 10 Maths Book

Written by Satish

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