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Locus of point of intersection of tangents at \mathrm{(a \cos \alpha, b \sin \alpha) \text { and }(a \cos \beta, b \sin \beta)}  for the ellipse \mathrm{\frac{x^2}{a^2}+\frac{y^2}{b^2}=1}  is, (given that (α – β) is a constant)

 

Option: 1

a circle


Option: 2

a straight line


Option: 3

an ellipse


Option: 4

a parabola

 


Answers (1)

best_answer

Point of intersection of tangents at \mathrm{(a \cos \alpha, b \sin \alpha) \text { and }(a \cos \beta, b \sin \beta)} is 

\mathrm{\left(a \frac{\cos \frac{\alpha+\beta}{2}}{\cos \frac{\alpha-\beta}{2}}, b \frac{\sin \frac{\alpha+\beta}{2}}{\cos \frac{\alpha-\beta}{2}}\right)}

\mathrm{\therefore \quad \text { required locus is } \frac{x^2}{a^2}+\frac{y^2}{b^2}=\sec ^2\left(\frac{\alpha-\beta}{2}\right)}

                                                             \mathrm{\text { [ } 8 \alpha-\beta \text { is given as constant }]}

which is the equation of an ellipse

 

Posted by

Pankaj Sanodiya

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