The sum of the focal distances of any point on the ellipse <span class="math-tex">\(\rm \dfrac{x^2}{a^2} + \dfrac{y^2}{b^2}=1, a<b\)</span>, with eccentricity e, is given by:
Here \(a < b\), so the major axis is along the y-axis and its length is \(2b\). The foci are \((0, \pm be)\).
For any point on an ellipse, the sum of its distances from the two foci equals the length of the major axis.
Sum of focal distances = \(2b\)
Answer: (B) 2b
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