Geometry

Question Analysis

This question focuses on using trigonometric functions, specifically the cosine function, in the context of similar right - angled triangles. The key is to find the cosine of ∠A by applying the side - length ratio rule for cosine in a right - triangle.

 

Key Concept Explanation:

In a right - triangle, for an acute angle , .

 

Step-by-Step Solution

In right - triangle  with , if  is corresponding to  (due to similarity):

The side adjacent to  is , and the hypotenuse is .

Using the formula , we get