Math Questions and Answers

Start Your Free Trial

Show, using algebra, that the formula  for a circle  is a special case of the formula  for an ellipse.

Expert Answers info

Eric Bizzell eNotes educator | Certified Educator

briefcaseTeacher (K-12)

calendarEducator since 2011

write3,149 answers

starTop subjects are Math, Science, and Business

The formula for a circle is `(x-h)^2+(y-k)^2=r^2` where the center of the circle is at (h,k) and the radius is r.

The formula for an ellipse is `((x-h)^2)/a^2+((y-k)^2)/b^2=1` where (h.k) is the center of the ellipse and a and b are the semi-major and simi-minor axes.

Assume we have an ellipse centered at (h,k) whose major and minor axis have equal length. This describes a circle centered at (h,k).

Then `((x-h)^2)/a^2+((y-k)^2)/a^2=1`

`(x-h)^2+(y-k)^2=a^2` by multiplying through by `a^2`

which is the formula for a circle centered at (h,k). Thus the formula for a circle is a special case of the formula for an ellipse.


check Approved by eNotes Editorial