We known that circumradius of triangle
`R=("Product of all sides")/(4xx"Area of triangle")` ltbr Consider point `P(a cos theta, b sin thea)` on the ellipse.
`:.` Circumrdius , `R=(a(1-ecostheta)xxa(1+ecostheta)xx2ae)/(4xx(1)/(2)b sin thetaxx2ae)`
`=(a^(2)(1-e^(2)cos^(2)theta))/(2b sin theta)`
`=(a^(2)(1-e^(2)(1-sin^(2)theta)))/(2b sin theta)`
`=(a^(2))/(2)(e^(2)sintheta+(b^(2))/(a^(2))"cosec"theta)`
`ge(a^(2))/(2b)xx(2be)/(a)ae`
`:.R_("min")=(a^(2))/(2b)xx(2be)/(a)=ae`