Question

An equation for a particular ellipse is
x^2/40+ y^2/b^2 = 1.
If this ellipse is also a circle, what is the relationship between b and the radius of the circle?

Answer 1

since this is also a circle, the coefficients of the x^2 term and y^2 terms must be equal...
in other words, b^2=40.

when you put this in standard form,
x^2 + y^2 = 40

can you tell me the radius of the circle now?

Answer 2

sqrt(40)