Answer: c2 = a2 - b2.
- A c2 = a2 + b2
- B c2 = a2 - b2
- C c2 = b2 - a2
- D c = a + b
Correct answer: B. c2 = a2 - b2
Explanation: For an ellipse, c2 = a2 - b2, since the foci lie inside the ellipse.
All four conics form a single family distinguished only by eccentricity: a circle is the most "closed" (e=0), an ellipse is an elongated closed curve, a parabola is the borderline open curve (e=1), and a hyperbola has two separate open branches (e>1).
Concept context
Study circles, parabolas, ellipses, and hyperbolas as curves formed by intersecting a plane with a double cone, with their standard equations and key properties.