OpenSAT

Draw a diagram of the circle with the chord and the radius to the chord. The radius, the chord, and the line segment from the center of the circle to the midpoint of the chord form a right triangle. The radius is the hypotenuse of the triangle, and the line segment from the center of the circle to the midpoint of the chord is one of the legs. Since the chord is 8 units long, the line segment from the center of the circle to the midpoint of the chord is 4 units long. Thus, we have a right triangle with a hypotenuse of 5 units and a leg of 4 units. Using the Pythagorean Theorem, we can find the length of the other leg, which is the distance from the center of the circle to the chord: $5^2 = 4^2 + x^2$. This gives us $x^2 = 9$, and so $x = 3$.