In below shown figure, PSSQ= PTTR and∠PST= ∠PRQ. Then ΔPQR 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 the equal angles)
i.e., ΔPQR is an isosceles triangle.