1.

If radii of director circles of `x^2/a^2+y^2/b^2=1 and x^2/a^2-y^2/b^2=1` are `2r and r` respectively, let `e_E and e_H` are the eccentricities of ellipse and hyperbola respectively, thenA. `2e_(h)^(2)-e_(e)^(2)=6`B. `e_(e)^(2)-4e_(h)^(2)=6`C. `4e_(h)^(2)-e_(e)^(2)=6`D. none of these

Answer» The equation of the director circles of ellipse and hyperbola are
`x^(2)+y^(2)=a^(2)+b^(2)` and `x^(2)+y^(2)=a^(2)-b_(1)^(2)` respectively.
`:.2r=sqrt(a^(2)+b^(2))` and `r=sqrt(a^(2)-b_(1)^(2))`
`=2sqrt(a^(2)-b_(1)^(2))=sqrt(a^(2)+b^(2))`
`implies4(a_(1)^(2)-b_(1)^(2))=a^(2)+b^(2)`
`implies4(1-(b_(1)^(2))/(a^(2)))=(1+(b^(2))/(a^(2)))`
`implies4{1-(e_(h)^(2)-1){=1+(1-e_(e)^(2))`
`implies8-4e_(h)^(2)=2-e_(e)^(2)implies4e_(h)^(2)-e_(e)^(2)=6`


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