Geometry

Question Analysis:  
This question involves using the Pythagorean Theorem in a square, where the diagonal divides it into two right triangles.  
The main focus is on finding the side length when the diagonal is given.  

Key Concept Explanation:  
For a square with side length s, the diagonal d follows:  
or  

Step-by-Step Solution:  
1. Given diagonal:    
2. Use the diagonal formula:  

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