Q15 of 63 Page 202

Find the distance between the directrices of the ellipse x2/36 + y2/20 = 1

Equation of an ellipse = , whereas


Length of latus rectum =


Length of minor axis = 2b


b2 = a2 (1 - e2) --------- (i)




From equation (i),


20 = 36 (1 - e2)






Directrices =


Distance between directrices =


Hence the distance between directrices is 18 units.


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