OpenSAT

Draw a diagram of the circle, the chord, and the radius from the center of the circle to the midpoint of the chord. This radius will be perpendicular to the chord, dividing the chord into two equal segments of length 4 units. The radius, the chord segment, and the distance from the center to the chord form a right triangle with a hypotenuse of 5 units and one leg of 4 units. By the Pythagorean Theorem, the distance from the center to the chord is $\sqrt{5^2 - 4^2} = \sqrt{9} = 3$ units.