Foci of an Ellipse c = √(a²−b²). Major a Minor b c 4 Step-by-step with your numbers: 1. Values used: 2. Major a = 5 3. Minor b = 3 4. c = 4 Did we solve your problem today? 👍 Yes 👎 No Thanks for the feedback! Distance center to focus. FAQ Circle? c=0. Related calculators Ellipse Calculator Area and approximate perimeter of an ellipse. Ellipse Calculator Find an ellipse's area, circumference and eccentricity.