10. Prove that the angle between the two tangents drawn from an external point to a circle is supplementary to the angle subtended by the line-segment joining the points of contact at the centre.
To prove -
Proof-
We have, PA and PB are two tangents, B and A are the point of contacts of the tangent to a circle. And ,
(since tangents and radius are perpendiculars)
According to question,
In quadrilateral PAOB,
OAP +
APB +
PBO +
BOA =
90 + APB + 90 +
BOA = 360
Hence proved