Draw a circle of radius 4.2 cm, and take any point on the circle. Draw the tangent at that point using the centre.

Radius of the circle = 4.2 cm

The steps of construction:

Step 1: With O as the center draw a circle of radius 4.2cm

Step 2: Take a point P on the circle and join OP.

Step 3: Draw an arc of a circle with center at P cutting OP at L.

Mark M and N on the arc such that ⌒LM = ⌒MN = LP

Step 4: LM = MN = LP

Step 5: Draw the bisector YP of the ∠MPN.

Step 6: Produce YP to X and get required tangent.

Thus, this is the resulting figure.