If you have found the coordinates, then the distance
between the points is just
√(difference in the Xs)² + (difference in the Ys)² .
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Part 2: No.
From the equation of the circle, the center is at the origin,
and the radius is 5.
Reason #1:
==> Since the distance between your points A and B is not 10,
AB can't be a diameter of the circle.
(If you got 10 or more for the length of AB, you made a mistake on the
coordinates of A or B, or on the distance between them.)
The line Y=1-x does not go through the origin.
(Write it as Y = -x + 1 . The Y-intercept is 1, not zero.)
Reason #2:
==> Since and the line AB doesn't go through the origin and the circle
is centered at the origin, AB doesn't go through the center of the circle,
so it can't be a diameter of the circle.
