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If a tangent to the ellipse x^{2}+4 y^{2}=4 meets the tangents at the extremities of its major axis at B and \mathrm{C}, then the circle with \mathrm{BC} as diameter passes through the point
Option: 1 (\sqrt{3}, 0)
Option: 2 (\sqrt{2}, 0)
Option: 3 (1,1)
Option: 4 (-1,1)

Answers (1)

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\frac{x^{2}}{4}+\frac{y^{2}}{1}= 1\Rightarrow a^{2}= 4,b^{2}= 1

Let point of Ellipse be P\left ( 2\cos \theta ,\sin \theta \right )

Equation of tangent : T = 0

\frac{x}{4}\cdot 2\cos \theta +y\cdot \sin \theta = 1

For point C, put x = 2 in this equation

y= \frac{1-\cos \theta }{\sin \theta }= \tan \frac{\theta }{2}

C\left ( 2,\tan \frac{\theta }{2} \right ) \\Similarly \: B\left ( -2,\cot \frac{\theta }{2} \right )\, \\\\Equation\; of\, circle\, with\, BC\, as\, diameter
\left ( x+2 \right )\left ( x-2 \right )+\left ( y-\cot \frac{\theta }{2} \right )\left ( y-\tan \frac{\theta }{2} \right )= 0
Cheking options, 1st option satisfies it

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Kuldeep Maurya

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