MCQ Practice Arena
Chords, Arcs and Cyclic Quadrilaterals — The Most Elegant Theorems in Class IX
Circles in Class IX is theorem-rich — equal chords equidistant from centre, angle in a semicircle is 90°, and cyclic quadrilateral properties are CBSE and NTSE staples. CBSE awards a 5-mark proof plus 1–2 MCQs from this chapter. The angle subtended by a chord at the centre is double that at any point on the remaining arc — this theorem and its corollaries produce the most MCQs.
Recall these cold before attempting MCQs — they appear in >70% of questions.
The most powerful theorem in this chapter: the angle at the centre is DOUBLE the angle at any point on the remaining arc. Use this to derive all other corollaries — semicircle angle (arc = 180° → centre angle = 180° → circumference angle = 90°), same segment angles (equal because they subtend the same arc). For cyclic quadrilateral MCQs, remember opposite angles sum to 180° — use this to find missing angles instantly.
Work through each rung in order — do not jump to Hard before mastering Easy.
Basic definitions, perpendicular bisector of chord, angle in semicircle
Central vs circumference angle, equal chord distances, cyclic quad angles
Multi-theorem circle problems, converse applications, exterior angle of cyclic quad
CBSE — prove theorem + numerical angle; NTSE — cyclic quad and chord problems
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