Step-by-Step Solution
Key Concept: The $(m-n)$ theorem relates angles and distances in elevation/depression problems using cotangent relationships
By the $(m - n)$ theorem, we have $30 \cot 60° = 10 \cot 45° - 20\cot(\frac{\pi}{2} + \alpha)$. This gives $10\sqrt{3} = 10 + 20 \tan \alpha$, so $2 \tan \alpha = \sqrt{3} - 1$.
Correct Answer: 3