Let the equation of the ellipse is:
ax2+by2=1
The equation of the normal to this ellipse at (ae,ab2) is:
a2aex−ae=ab2b2y−ab2 →(1)
This normal passes through (0,−b) according to given condition.
Substitute x=0,y=−b in equation (1)
a2ae0−ae=ab2b2−b−ab2
Simplify
−a2=−ab−b2 →(2)
Since e2=1−a2b2
So, a2b2=1−e2
Therefore, b2=a2(1−e2)
Substitute b2 in equation (2)
−a2=−ab−a2(1−e2)
Simplify
a2=ab+a2−a2e2
ab=a2e2
b=ae2
So,
b2=a2e4
And we know that
b2=a2(1−e2)
Therefore,
a2e4=a2(1−e2)
Simplify
e4+e2−1=0
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