In △DMUand△BMV
(i) Since AB∥DC AND DB is transversal,
∠UDM=∠MBV (alternate angles)
Since AB∥DC AND UV is transversal,
∠DUM=∠MVB (alternate angles)
∠DMU=∠VMB (vertically opposite angles)
∴△DMU∼△BMV (AAA similarity criterion)
Hence, proved.
(ii) Since △DMU∼△BMV,
By CPST,
DMBM=DUBV
∴DM×BV=DU×BM
Hence, proved.