In the fig 6.21, A, B and C are points on OP, OQ and OR respectively such that AB || PQ and AC || PR. Show that BC || QR.
In ΔOPQ, AB || PQ (Given)
∴ OA/AP = OB/BQ ...(i) [By using Basic Proportionality Theorem]
In ΔOPR, AC || PR (Given)
∴ OA/AP = OC/CR ...(ii) [By using Basic Proportionality Theorem]
From equation (i) and (ii), we get
OB/BQ = OC/CR
In ΔOQR, BC || QR. [By converse of Basic Proportionality Theorem].
