1
∠A + ∠C = 180° and ∠B + ∠D = 180°
2
Exterior angle = interior opposite angle
FORMULA CHAPTER
Chapter 10 – Theorems Related to Cyclic Quadrilateral
WBBSEClass 10Mathematics2 formulas
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Opposite Angles of a Cyclic Quadrilateral
∠A + ∠C = 180° and ∠B + ∠D = 180°
SymbolMeaningUnit
∠A, ∠B, ∠C, ∠Dinterior angles°
Worked example
Given: ∠A = 110° Calculation: ∠C = 180° − 110° Answer: ∠C = 70°.
Exterior Angle of a Cyclic Quadrilateral
Exterior angle = interior opposite angle
SymbolMeaningUnit
exterior angleangle formed by an extended side°
Worked example
Given: exterior angle = 75° Calculation: opposite interior angle = 75° Answer: 75°.