Answer:
170°
Step-by-step explanation:
Let a be the distance from Los Angeles to Chicago = 1744 miles, b be the distance from Chicago to New York = 714 miles and c be the distance from New York to Los Angeles = 2451 miles.
A is the angle opposite to side a, B is the angle opposite to side b and C is the angle opposite to side c.
Therefore the angle at Chicago is C.
From cosine rule:
c² = a² + b² - 2ab × cos (C)
2ab × cos (C) = a² + b² - c²
cos (C) = (a² + b² - c²) / 2ab
Substituting:
cos (C) = (1744² + 714² - 2451²) / 2×1744×741
cos (C) = -0.986
C = cos⁻¹ (- 0.986) = 170°
