Classes IX & X Mathematics
Chapter 9: Circles
Standard NCERT & CBSE aligned study curriculum. Master concepts, track accuracy, revise weak areas, and challenge yourself with 9 customized practice modes.
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Syllabus Sections
Key Formulas & Equations
Click Copy to duplicateDouble Angle Theorem
\theta_{center} = 2 \theta_{boundary}
Angle subtended by arc at center is twice angle at circumference.
Cyclic Quadrilateral interior sum
A + C = 180^\circ \land B + D = 180^\circ
Opposite angles of cyclic quadrilaterals are supplementary.
Related Formulas from Adjacent Chapters
Heron's Formula
A = \sqrt{s(s-a)(s-b)(s-c)}
[From Heron's Formula] Calculates triangle area using semi-perimeter s and sides a, b, c.