Theorems

Theorem 9.1
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Theorem 9.2 Important

Theorem 9.3 Important

Theorem 9.4

Theorem 9.5 Important

Theorem 9.6

Theorem 9.7 Important

Theorem 9.8

Theorem 9.9 Important

Theorem 9.10

Theorem 9.11 Important

Angle in a semicircle is a right angle Important

Only 1 circle passing through 3 non-collinear points Deleted for CBSE Board 2025 Exams

Last updated at April 16, 2024 by Teachoo

Theorem 9.1 Equal chords of a circle subtend equal angles at the center. Given: A circle with center O. AB and CD are equal chords of circle i.e. AB = CD To Prove : ∠AOB = ∠DOC Proof : In ΔAOB & ΔDOC AO = OD AB = CD OB = OC ∴ ∆AOB ≅ ∆ DOC ∴ ∠ AOB = ∠ DOC Hence, Proved.