1.

If the latus rectum of an ellipse is equal to the half of minor axis, then find its eccentricity.

Answer» Consider the equation of the ellipse is `(x^(2))/(a^(2))+(y^(2))/(b^(2))=1`
`therefore`Length of major axis=2a
Length of minor axis=2b
and length of latusrectum=`(2b^(2))/a`
Given that, `(2b^(2))/a=(2b)/2`
`rArr` a=2b`rArr`b=a/2
We know that, `b^(2)=a^(2)(1-e^(2))`
`rArr (a/2)^(2)=a^(2)(1-e^(2))`
`rArr(a^(2))/4=a^(2)(1-e^(2))`
`rArr1-e^(2)=1/4`
`rArre^(2)=1-1/4`
`therefore e=sqrt(3/4)=sqrt(3/2)`


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