Draw a circle of diameter 6.4 cm. Take a point R at a distance equal to its diameter from the centre. Draw tangents from point R.

Construction steps:
1.Draw a circle of radius = 6.4/ 2 = 3.2 cm with centre O.
2. Mark a point R in the exterior of the circle so that OR = 6.4 cm.
3. Draw segment OR. Draw a perpendicular bisector of OR. Mark its midpoint M.
4. Draw a circle with radius OM and centre M.
5. Mark the point of intersection of the two circles as A and B.
6. Draw lines RA and RB.
RA and RB are the required tangents from point R.