Two circles intersect at P and Q. Through P diameters PA and PB of the two circles are drawn. Show that the points A, Q and B are collinear.
Two circles intersect at P and Q. Through P diameters PA and PB of the two circles are drawn. Show that the points A, Q and B are collinear.

Selina Solutions Concise Class 10 Maths Chapter 17 ex. 17(A) - 29

Solution:

According to the given question,

Let

    \[O\text{ }and\text{ }O\]

be the centres of two intersecting circles, where points of the intersection are

    \[P\text{ }and\text{ }Q\text{ }and\text{ }PA\text{ }and\text{ }PB\]

are their diameters respectively.

Join

    \[PQ,\text{ }AQ\text{ }and\text{ }QB\]

Hence,

    \[\angle AQP\text{ }=\text{ }{{90}^{o}}~and\angle BQP\text{ }=\text{ }{{90}^{o}}\]

[Angle in a semicircle is a right angle]

Adding both these angles we get

    \[\angle AQP\text{ }+\angle BQP\text{ }=\text{ }{{180}^{o}}\]

    \[\angle AQB\text{ }=\text{ }{{180}^{o}}\]

Therefore, the points

    \[A,\text{ }Q\text{ }and\text{ }B\]

are collinear.