Geometry

Question Analysis  

The question asks in which quadrants cos θ is positive, focusing on the sign of cosine related to the x-coordinate in the unit circle.  

Key Concept Explanation  

Cos θ corresponds to the x-coordinate on the unit circle:  

Positive where x > 0 (Quadrants I and IV).  

Negative where x < 0 (Quadrants II and III).  

ASTC rule: Cos is positive in Quadrant I (All) and IV (Calculus).  

Step-by-Step Solution  

1. Recall the x-coordinate sign in each quadrant:  

Q1: x > 0 → Cos (+)  

Q2: x < 0 → Cos (-)  

Q3: x < 0 → Cos (-)  

Q4: x > 0 → Cos (+)  

2. Thus, cos θ is positive in Quadrant I and IV.  

Option Analysis  

Quadrant I and II: Q2 has Cos (-)(...