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, with the radius as the hypotenuse and the line segment from the center of the circle to the midpoint of the chord as one leg. Since the chord is 8 centimeters long, the line segment from the center of the circle to the midpoint of the chord is 4 centimeters long. Applying the Pythagorean theorem, we get that the distance from the center of the circle to the chord is $\sqrt{5^2-4^2} = \sqrt{9} = 3$ centimeters.