Construct a parallelogram ABCD, if :

lengths of diagonals AC and BD are 6.3 cm and 7.0 cm respectively, and the angle between them is 45°.

Steps:

1. Draw AC = 6.3 cm.

2. Locate the mid-point O of AC by drawing its perpendicular bisector.

3. Through O, construct a line EOF so that angle EOC = 45°.

4. From EF, cut OD = $\dfrac{BD}{2}$ = $\dfrac{7}{2}$ = 3.5 cm and also OC = $\dfrac{BD}{2}$ = $\dfrac{7}{2}$ = 3.5 cm

5. Join AB, BC, CD and DA.

Hence, ABCD is the required parallelogram.