AB = 5.8 cm, diagonal AC = 8.2 cm and diagonal BD = 6.2 cm.

Steps of construction : 1. Draw a line segment AB = 5.8 cm 2. Since diagonals of a parallelogram bisect each other; construct triangle OBC, such that : OB = = 3.1 cm OA = = 4.1 cm 3. Produce BO upto D, such that OD = OB = 3.1 cm and produce AO upto C, such that OC = OA = 4.1 cm. 4. Join BC, CD and AD. Hence, ABCD is the required parallelogram.