Given: Equation of ellipse is
9x2+4y2=36 The given equation of ellipse can be re-written as
+=1 As we can see that, the given ellipse is a vertical ellipse.
So, by comparing the equation
+=1 with
+=1 we get
⇒a2=9 and
b2=4 As we know that, eccentricity of ellipse is given by
e=√1− ⇒e=√1−= As we know that, for a vertical ellipse equation of directrix is given by
y=± So, the distance between the directrices is given by
=