Since the chord and the diameter are perpendicular, we know that the diameter bisects the chord. This fact will help us find lengths later in the exercise. Since the diameter is 18, the radius must be 9. if we draw the radius HL we can create the right triangle △ LPH.
Since the chord it bisected, we can determine the length of one of the triangle's legs.
Chord length/Bisected → 12/2=6
To determine HP, we will substitute the known leg and hypotenuse into the Pythagorean Theorem.
