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

Solution: Please refer to video for the diagram.
Let tangents at $A$ and $B$ intersect at point P.
We know tangent at any point at circle, make an angle of ${90}^{\circ }$ with a line at center of circle.
So, here, $\angle BAP=\angle ABP={90}^{\circ }$
Then, in $\Delta ABP$,
$\angle PAB\frac{+}{+}ABP+\angle APB={180}^{\circ }$
$90+90+\angle APB=180$
$\angle APB=0^{\circ }$
As, angle created by two tangents$AP$ and $BP$ of circle is $0^{\circ }$, which means $AB$ is parallel to $BP$.