Areas of Parallelograms and Triangles

Question

In figure, ∠QPR = ∠PQR and M and N are respectively points on sides QR and PR of ∆PQR, such that QM = PN. Prove that OP = OQ, where O is the point of intersecting of PM and QN.


Answer

Given: ∠QPR = ∠PQR and M and N are respectively points on side QR and PR of ∆PQR, such that QM = PN.
To Prove: OP = OQ, where O is the point of intersection of PM and QN.
Proof: In ∆PNQ and ∆QMP,
PN = QM    | Given
PQ = QP    | Common
∠QPN = ∠PQM    | Given
∴ ∆PNQ ≅ ∆QMP
| SAS congruence rule
∴ ∠PNQ = ∠QMP    | CPCT
Again, in ∆PNO and ∆QMO,
PN = QM    | Given
∠PON = ∠QOM
| Vertically opposite angles
∠PNO = ∠QMO | Proved above
∴ ∆PNO ≅ ∆QMO
| AAS congruence rule
∴ OP = OQ    | CPCT

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