If the length of a chord of a circle If the length of a chord of a circle with equation $x^2+y^2=100$ is $16$ units, how far is the chord from the centre?
My Attempt;
$$x^2+y^2=100$$
$$x^2+y^2=10^2$$
So, centre of circle $=(0,0)$.
How do I move further? Please help.
Thanks.

Without loss of generality, suppose the chord is vertical, and to the right of the origin. Then its $x$ coordinate is the distance from the center. You also know that the endpoints of the chord, $(x,\pm8)$ are on the circle -- this gives you a quadratic equation in $x$ that you can solve:
$$ x^2+8^2=100 $$
