Given:

Radius of circle (say PO) = 4 cm

Let AB ∥ CD be two tangents which meets the circle at P and Q respectively. And, O be the center of circle.

Property: The tangent at a point on a circle is at right angles to the radius obtained by joining center and the point of tangency.

By above property, we can say that distance between two parallel tangents of a circle is equal to its diameter.

Therefore,

PQ = 2 × PO

= 2 × 4 cm

= 8 cm

Hence, Distance between tangents = 8 cm