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O is the incentre of ΔPQR and ∠QPR = 50°, then O is the incentre of ΔPQR

the measure of ∠QOR is :

a

125°

b

100°

c

130°

d

115°

Answer : Option D
Explanation :

QPR=50\angle \mathrm{QPR}=50^{\circ}

PQR+PRQ=18050=130\therefore \angle \mathrm{PQR}+\angle \mathrm{PRQ}=180^{\circ}-50^{\circ}=130^{\circ}

12PQR+12PRQ=65\therefore \frac{1}{2} \angle \mathrm{PQR}+\frac{1}{2} \angle \mathrm{PRQ}=65^{\circ}

The point of intersection of internal bisectors of angles is in-centre.

OQR=12PQR;\therefore \quad \angle \mathrm{OQR}=\frac{1}{2} \angle \mathrm{PQR} ;

ORQ=12PRQ\angle \mathrm{ORQ}=\frac{1}{2} \quad \angle \mathrm{PRQ}

In OQR,OQR+QOR+ORQ=180\triangle \mathrm{OQR}, \angle \mathrm{OQR}+\angle \mathrm{QOR}+\angle \mathrm{ORQ}=180^{\circ}

QOR=18065=115\Rightarrow \angle \mathrm{QOR}=180^{\circ}-65^{\circ}=115^{\circ}

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