In the figure shown below, PSSQ=PTTR and ∠PST=∠PRQ. Then △PQR is
It is given that
PSSQ=PTTR
So, ST∥QR
∴∠PST=∠PQR [Corresponding Angles]
Also, it is given that
∠PST=∠PRQ
So,∠PRQ=∠PQR
Therefore, PQ=PR [Sides opposite to the equal angles]
i.e., △PQR is an isosceles triangle.