2 circles meet @ points A & B. Points X & Y of these circles are diametrically opposite to point A.

Prove that X, Y and B are collinear.

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- Aug 21st 2010, 06:11 AMthe undertakercircle geomtry II
2 circles meet @ points A & B. Points X & Y of these circles are diametrically opposite to point A.

Prove that X, Y and B are collinear. - Aug 21st 2010, 08:44 AMmathaddict
Diametrically opposite means opposite along the diameter. As usual, make a sketch.

You will need to use the fact that the angle in a semicircle is 90 degree.

so angle XBA=angle YBA=90 and that is the sum of angles along a straight line.

What can you deduce from here?