Question 1188600
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The radius that is perpendicular to the chord bisects the chord.  So the portion of that radius from the center to the chord, half of the chord, and a radius to the end of the chord form a right triangle; the lengths of the legs are 3 (given) and 9 (half of the chord length), and the hypotenuse is the radius of the circle.<br>
Use the Pythagorean Theorem to answer the question.<br>