The tangents from which of the following points to the ellipse 5x2+4y2=20 are perpendicular:
A
(√5,2√2)
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B
(2√2,1)
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C
(√5,−1)
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D
(√5,1)
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Solution
The correct option is B(2√2,1)
The locus of the point of intersection of the tangents to the ellipse which meet at right angle, is a circle. This circle is called the "director circle" of the ellipse.
Points lies on director circle.
x2+y2=a2+b2=9
Therefore, from the options (2√2,1) lies on director circle.