O T (contact) P OT ⊥ PT PA = PB (tangent lengths)
Chapter 10 · Class X Mathematics · NCERT Exercises

Circles — Exercises

Tangents · Chord Properties — All Circle Theorems Exercise-Solved

📂 3 Exercises 📝 21 Questions 🎓 Moderate-High

Exercise Index

3 exercise files · 21 total questions

Chapter at a Glance

CBSE BoardsNTSEOlympiad
9 Concepts
6 Formulas
Moderate-High Difficulty
6–8% Weightage

Before You Begin

Prerequisites

  • Circle basics (Class IX) — chord, arc, sector
  • Congruence of triangles
  • Pythagoras Theorem

Have Ready

  • 🔧Compass for accurate circle drawing
  • 🔧Ruler
  • 🔧NCERT circle theorems card

Exercise Topic Map

Exercise 10.1 Tangent ⊥ radius at point of contact; two tangents from external point are equal
Exercise 10.2 PA=PB (tangent lengths); use congruent triangles (SSS/RHS) in proofs; angle in alternate segment
Miscellaneous AB+CD=AD+BC for quadrilateral circumscribed about circle; multi-tangent proofs

Key Formulae — Recall Before Solving

\(OT \perp PT \quad \text{(radius} \perp \text{tangent at contact point)}\)
\(PA = PB \quad \text{(tangent lengths from external point P are equal)}\)
\(OP^2 = OA^2 + AP^2 \quad \text{(right angle at A)}\)
\(AB + CD = AD + BC \quad \text{(quadrilateral circumscribed about circle)}\)

NCERT Solving Method

Step 1 — Draw a clear diagram; mark the centre O, point of contact T, and external point P. Step 2 — For tangent length problems: form right triangle OTP; apply Pythagoras. Step 3 — For proofs: use the two key theorems — (i) radius⊥tangent, (ii) tangent lengths equal; combine with congruent triangles. Step 4 — Circumscribed quadrilateral: immediately write AB+CD=AD+BC as given; use algebraically.

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