Given :
A circle with center O has diameter AB. PQ and RS are the tangents at the points A and B.
To prove: PQ || RS.
Proof : PQ is the tangents to the circle at the point A. OA is radius
∴∠1 = 90°
Similarly RS ⊥ OB
∴∠2 = 90°
Now, ∠1 = ∠2
But this ¡s alternate angle of two parallel lines, when a transversal cuts them.
∴ PQ || RS
Hence, the tangents drawn at the ends of a diameter of a circle are parallel.
