Algebra-2

Question Analysis
This problem evaluates the understanding of the properties of a 30-60-90 triangle and the cosine function.

Key Concept Explanation
In a 30-60-90 triangle, the sides are in the ratio 1:√3:2. The cosine of 30 degrees is , but in this context, we use the known ratio of the sides.

Step-by-step Solution
1. Identify the given values: hypotenuse = 20 units.
2. Use the property of a 30-60-90 triangle: the adjacent side to the 30-degree angle is half the hypotenuse.
3. Calculate the adjacent side: