CON008 · Conic sections · Classes 11–12
Ellipse eccentricity
Eccentricity e = c/a measures how stretched an ellipse is: 0 is a circle, close to 1 is long and thin.
e = c/aEllipse eccentricity
📐 Formula
e = c/a = √(1 − b²/a²)
✏️ Worked example
a = 5, b = 3: c = 4, e = 0.8.
🌍 Where it is used
Comparing orbits: Earth's e ≈ 0.017, Halley's comet e ≈ 0.97.
❓ Quick check
An ellipse with e = 0 is a…
🏋️ Practice
Easya = 10, b = 6. e?
Answer: 0.8
Mediuma = 2, e = 0.5. c?
Answer: 1
ChallengeWhich is rounder: e = 0.1 or e = 0.9?
Answer: e = 0.1