Let \(PQ\) be a diameter of a circle. If tangents are drawn at \(P\) and \(Q\), show that these tangents are parallel.
Proof:
\(P\) and \(Q\) are point of contacts of tangent lines and respectively.
\(O\) is the centre of circle.
We know that, the at any point of a circle is to the through the point of contact.
\(OP\perp\)
\(OQ\perp \) and \(PQ\) is diameter.
\(∠PQm + ∠QPl = \)\(^° + \)\(^° = \)\(^°\)
As, sum of adjacent angles is , hence opposite sides are .
Therefore, the tangents drawn at the ends of a diameter of a circle are parallel.