Prove that the tangent drawn at the mid-point of an arc of a circle is parallelto the chord joining the end points of the arc.
Solution
Let mid-point of arc is C and DCE be the tangent to the circle.
Construction: Join AB, AC and BC.
Proof: In ABC
AC = BC
[ sides opposite to equal angles are equal]
Here DCF is a tangent line
[ angle in alternate segments are equal]
…..(ii) [From equation (i)]
But Here and are alternate angels.
equation (ii) holds only when AB||DCE.
Hence the tangent drawn at the mid-point of an arc of a circle is parallel to the chord joining the end points of the arc.
Hence Proved.