Thread: deductive geo

The diagram shows the triangle PQR with sides PQ and PR produced to Y and Z respectively so that PQ . PY=PR . PZ . Prove that triangles PQR and PZY are similar .

PQ/PZ=PR/PY

is this sufficient to prove that they are similar ??

You have to add that

In this case QR is known as an "antiparallel" to YZ.