Answer:

Firstly, draw a circle and connect two points A and B such that AB becomes the circle’s diameter. Now, at points A and B, draw two tangents PQ and RS, respectively.

Both radii, AO and OB, are now perpendicular to the tangents.

As a result, OA perpendicular to PQ and OB is perpendicular to RS

Therefore,  ∠OAP = ∠OAQ = ∠OBR = ∠OBS = 90°

Angles OBR and OAQ are alternate interior angles in the figure above.

Also we can say that, ∠OBR = ∠OAQ and ∠OBS = ∠OAP since they are also alternate interior angles.

As a result, lines PQ and RS will be parallel to each other. (Hence Proved).