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प्रश्न
If I is the incentre of triangle ABC and AI when produced meets the cicrumcircle of triangle ABC in points D . if ∠BAC = 66° and ∠ABC = 80°. Calculate : ∠IBC
उत्तर
Join DB and DC , IB and IC ,
∠ BAC = 66° , ∠ ABC = 80° , I is the incentre of the Δ ABC,
Since I is the incentre of ∆ABC, IB bisects ∠ABC
∴ ∠ IBC = `1/2` ∠ABC = `1/2 xx 80° = 40° `
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