Question

how to prove that three points on two circles are collinear​

Answer 1

Hey mate!
Here's the solution....

$<u>Contstruction</u>$: Join AB, BC, and BD.

$<u>Proof</u>$: As we know, angle subtended by the diameter of a circle is 90°

So, <ABC=90°,because <ABC is is subtened by diameter AC.

And, <ABD=90°,because <ABD is is subtened by diameter AD.

<CBD=<ABC+<ABD
=90°+90°
=180°

Therefore, CBD is a straight line, and points C, B and D are collinear.
....Hence, proved.

I hope it helps you!!