The midpoints of the adjacent sides of a quadrilateral will form a__________.
parallelogram
Let ABCD be the quadrilateral and let P, Q, R and S be the midpoints of sides AB, BC, CD and DA respectively.
In ∆CDB, RQ ll DB and RQ = 12 DB (By mid point theorem)
In ∆ ADB, SP ll DB and SP = 12 DB ( By mid point theorem)
Combining these two, RQ ll SP and RQ ll SP
Since a pair of opposite sides are equal and parallel, we can say that PQRS is a parallelogram.