Step 1: Find the sine of angle C:
In the right triangle \(ADC\) (right angle at \(D\)), \(\sin C = \dfrac{AD}{AC} = \dfrac{3}{9} = \dfrac{1}{3}\).
Step 2: Use the law of sines on side AB:
In triangle \(ABC\), \(\dfrac{AB}{\sin C} = 2R\), where \(R\) is the circumradius. So \(2R = \dfrac{17.5}{1/3} = 52.5\).
Step 3: Find R:
\(R = \dfrac{52.5}{2} = 26.25\) cm.
Step 4: Check using angle B:
In the right triangle \(ABD\), \(\sin B = \dfrac{3}{17.5} = \dfrac{6}{35}\). Then \(2R = \dfrac{AC}{\sin B} = \dfrac{9 \times 35}{6} = 52.5\), so \(R = 26.25\) cm again.
Final Answer:
The correct option is (3): \(26.25\).