The Total solution for NCERT class 6-12
In ΔQTR, ∠TRS is an exterior angle.
∠QTR + ∠TQR = ∠TRS
∠QTR = ∠TRS − ∠TQR (1)
For ΔPQR,∠PRS is anexternal angle.
∠QPR + ∠PQR = ∠PRS
∠QPR + 2∠TQR = 2∠TRS (AsQT and RT are angle bisectors)
∠QPR = 2(∠TRS − ∠TQR)
∠QPR = 2∠QTR [By using equation (1)]