Question 71136
I get {{{4*sqrt(10)}}}
The chord is 3 cm from the center. Draw a radius through the center of 
the chord. It will be perpendicular to the chord.
Now draw a radius to one of the intersections of the chord with the circle
You are given that the radius = 7
Now you have a length of 3 cm to the center of the chord, whiich is a
leg of a right triangle.
The hypotenuse is the radius = 7
(1/2 the chord) = {{{sqrt(7^2 - 3^2)}}}
{{{sqrt(49 - 9)}}}
{{{sqrt(40)}}}
(1/2 the chord) = {{{2*sqrt(10)}}}
So, the chord = {{{4*sqrt(10)}}}