In figure, ∠x = ∠y and PQ = PR. Prove that PE = RS.

Given: In figure, ∠x = ∠y and PQ = PR
To Prove: PE = RS
Construction: Join PR
Proof: In ∆PQR,
∵ PQ = QR | Given
∴ ∠QRP = ∠QPR
| Angles opposite to equal sides of a triangle are equal
⇒ ∠ERP = ∠SPR ...(1)
In ∆PER and ∆RSP,
∠ERP = ∠SPR From (1)
∠REP = ∠PSR | Given
PR = RP | Common
∴ ∆PER ≅ ∆RSP
| AAS congruence rule
∴ PE = RS | CPCT