Triangle \( \triangle OMN \) with \( \angle O = 15^\circ \), \( \angle M = 120^\circ \), and \( OM = 11 \).
Step 2: Calculate \( \angle N \)
Use the fact that the sum of angles in a triangle is \( 180^\circ \).
\[ \angle N = 180^\circ - \angle O - \angle M \]
\[ \angle N = 180^\circ - 15^\circ - 120^\circ \]
\[ \angle N = 45^\circ \]
Step 3: Apply the Law of Sines to Find \( ON \)
The Law of Sines states:
\[ \frac{ON}{\sin(\angle M)} = \frac{OM}{\sin(\angle N)} \]
\[ \frac{ON}{\sin(120^\circ)} = \frac{11}{\sin(45^\circ)} \]
\[ \frac{ON}{\frac{\sqrt{3}}{2}} = \frac{11}{\frac{\sqrt{2}}{2}} \]
\[ ON \cdot \frac{\sqrt{2}}{2} = 11 \cdot \frac{\sqrt{3}}{2} \]
\[ ON \cdot \sqrt{2} = 11 \sqrt{3} \]
\[ ON = \frac{11 \sqrt{3}}{\sqrt{2}} \]
\[ ON = 11 \sqrt{\frac{3}{2}} \]