In the given figure ∠PQR = ∠PRQ, then prove that ∠PQS = ∠PRT.
In the figure, ST is a straight line and its angle is 180°
So, ∠PQS + ∠PQR = 180° ----(1)
And ∠PRT + ∠PRQ = 180°-----(2)
From the two equations, we get
∠PQS + ∠PQR = ∠PRT + ∠PRQ
Given that,
∠PQR = ∠PRQ
⇒ ∠PQS + ∠PRQ = ∠PRT + ∠PRQ
⇒ ∠PQS = ∠PRT + ∠PRQ -∠PRQ
⇒ ∠PQS = ∠PRT
So, ∠PQS = ∠PRT is proved.