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Question -

In a Δ ABC, the internal bisectors of ∠B and ∠C meet at P and the external bisectors of ∠B and ∠C meet at Q, Prove that ∠BPC + ∠BQC = 180°.



Answer -

In the given problem, BP and CP arethe internal bisectors of  respectively. Also, BQ and CQ arethe external bisectors of respectively. Here, we need toprove:

We know that if the bisectors of anglesand of ΔABC meetat a point then 

Thus, in ΔABC

 ……(1)

Also, using the theorem, “if the sides AB and AC of a ΔABC are produced, and theexternal bisectors of  and meet at O, then 

Thus, ΔABC

BQC=90°−12A        ......(2)BQC=90°-12A        ......2                

Adding (1) and (2), we get

Thus, 

Hence proved.

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