Geometry

Question Analysis  

Determine the Quadrant I angle where , using 45-45-90 triangle properties and unit circle coordinates.  

 

Key Concept Explanation  

In a 45-45-90 triangle, for .  

On the unit circle, this corresponds to the -coordinate , unique to 45°.  

 

Step-by-Step Solution  

1. Recall cosine values for special angles:  

, , , .  

2. Match the given value: corresponds to

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