KeerthanaPosted on O is the incentre of ΔPQR and ∠QPR = 50°, then O is the incentre of ΔPQR the measure of ∠QOR is : a125° b100° c130° d115° Answer : Option DExplanation : ∠QPR=50∘\angle \mathrm{QPR}=50^{\circ}∠QPR=50∘ ∴∠PQR+∠PRQ=180∘−50∘=130∘\therefore \angle \mathrm{PQR}+\angle \mathrm{PRQ}=180^{\circ}-50^{\circ}=130^{\circ}∴∠PQR+∠PRQ=180∘−50∘=130∘ ∴12∠PQR+12∠PRQ=65∘\therefore \frac{1}{2} \angle \mathrm{PQR}+\frac{1}{2} \angle \mathrm{PRQ}=65^{\circ}∴21∠PQR+21∠PRQ=65∘ The point of intersection of internal bisectors of angles is in-centre. ∴∠OQR=12∠PQR;\therefore \quad \angle \mathrm{OQR}=\frac{1}{2} \angle \mathrm{PQR} ;∴∠OQR=21∠PQR; ∠ORQ=12∠PRQ\angle \mathrm{ORQ}=\frac{1}{2} \quad \angle \mathrm{PRQ}∠ORQ=21∠PRQ In △OQR,∠OQR+∠QOR+∠ORQ=180∘\triangle \mathrm{OQR}, \angle \mathrm{OQR}+\angle \mathrm{QOR}+\angle \mathrm{ORQ}=180^{\circ}△OQR,∠OQR+∠QOR+∠ORQ=180∘ ⇒∠QOR=180∘−65∘=115∘\Rightarrow \angle \mathrm{QOR}=180^{\circ}-65^{\circ}=115^{\circ}⇒∠QOR=180∘−65∘=115∘ Rate This:NaN / 5 - 1 votesAdd comment