8. ABCD is a rectangle formed by the points A(–1, –1), B(– 1, 4), C(5, 4) and D(5, – 1). P, Q, R and S are the mid-points of AB, BC, CD and DA respectively. Is the quadrilateral PQRS a square? a rectangle? or a rhombus? Justify your answer.
From the figure:
P is the mid-point of side AB.
Therefore, the coordinates of P are,
Similarly, the coordinates of Q, R and S are: respectively.
The distance between the points P and Q:
and the distance between the points Q and R:
Distance between points R and S:
Distance between points S and P:
Distance between points P and R the diagonal length:
Distance between points Q and S the diagonal length:
Hence, it can be observed that all sides have equal lengths. However, the diagonals are of different lengths.
Therefore, PQRS is a rhombus.