Given: Two ║gm ABCD and PQRS with equal base AB and PQ and between the same parallels, AQ and DR.
To prove: ar( ║gm ABCD) = ar( ║gm PQRS).
Construction: Draw AL ⊥ DR and PM ⊥ DR.
Proof : AB ║ DR, AL ⊥ DR and PM ⊥ Dr
∴ AL = PM.
∴ ar( ║gm ABCD) = AB × AL
= PQ × PM [∵AB = PQ and AL = PM]
= a( ║gm PQRS).
