Diagonal AC = 6.4 cm, diagonal BD = 8.2 cm and angle between the diagonals = 60°.

Steps of construction :

1. Draw a line segment AC = 6.4 cm and locate its mid-point O.

2. Draw line BOD such that ∠DOC = 60° and OB = OD = $\dfrac{1}{2} BD = \dfrac{1}{2} \times 8.2$ cm = 4.1 cm.

3. Join AB, BC, CD and DA.

Hence, ABCD is the required parallelogram.