5. Prove that the perpendicular at the point of contact to the tangent to a circle passes
through the center
Answers
let angle qpb=90degree_(1)
as op perpendicular ab
angle opb = 90 degree_(2)
from 1 and 2
angle qpb= angle opb
which is not possible
therefore, our supposition is wrong hence perpendicular at a point of contact ti the tangent to a circle passes through the centre
Solution:
First, draw a circle with center O and draw a tangent AB which touches the radius of the circle at point P.
To Pr oof: PQ passes through point O.
Now, let us consider that PQ doesn’t pass through point O. Also, draw a CD parallel to AB through O. Here, CD is a straight line and AB is the tangent.
From the above diagram, PQ intersects CD and AB at R and P respectively.
AS, CD ∥ AB,
Here, the line segment PQ is the line of intersection.
Now angles ORP and RPA are equal as they are alternate interior angles
So, ∠ORP = ∠RPA
And,
∠RPA = 90° (Since, PQ is perpendicular to AB)
∠ORP = 90°
Now, ∠ROP+∠OPA = 180° (Since they are co-interior angles)
∠ROP+90° = 180°
∠ROP = 90°
Now, it is seen that the △ORP has two right angles which are ∠ORP and ∠ROP. Since this condition is impossible, it can be said the supposition we took is wrong.