Answer:
Let's imagine this is the diagram for the question,
•
3*440= / |
/ |
1320mi ↑ |
↑ ↓
/ ↓
/ |
• ) 89⁰ |
\ | "x" miles
\ ↑
\ ↑
↓ |
↓ |
3*420= \ |
1260 mi \ |
•
From the Cosine Rule: x² = y² + z² - 2 y z cos X⁰
x² = 1320² + 1260² - 2 * 1320 * 1260 * cos 89⁰ =
1742400 + 1587600 - 3326400 * cos 89⁰ = 3271946315
x ≈ 1809 mi
Hence, the planes are 1809 miles from each other 3 hours after takeoff?