Prove that the tangents drawn at the ends of a diameter of a circle are parallel.

Tangents \(\displaystyle l\) and \(\displaystyle m\) are drawn at the end points A and B of the diameter AB of the circle \[\begin{aligned} & \angle 1=90^{\circ}, \angle 2=90^{\circ} \\ & \therefore \angle 1=\angle 2 \end{aligned} \] But these are alternate interior angles. \[\therefore l \| m \]