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Pls solve this question as soon as possible of ellipse chapter

Rohan Mittal , 3 Years ago
Grade 12th pass
anser 1 Answers
Aman Tomar

Last Activity: 3 Years ago

As the normals are perpendicular, therefore the corresponding tangents are also perpendicular. So they must intersect on the director circle which is given by x 
2
 +y 
2
 =a 
2
 +b 
2
 =A 
2
  (say)
Any point P on the director circle may be taken as, (Acosθ,Asinθ)
Let the equation to the ellipse be  
2
 
2
 
 + 
2
 
2
 
 =1
So the polar of P w.r.t. the ellipse will be  
2
 
Axcosθ
 + 
2
 
Aysinθ
 =1
The intersection of the perpendicular normals may be given by the equation
So putting l= 
2
 
Acosθ
  and m= 
2
 
Asinθ
  we get,
x=(a 
2
 −b 
2
 ) 
2
 
Acosθ
  
2
 
2
 +b 
2
 
 −cos 
2
 θ
1− 
2
 
(a 
2
 +b 
2
 )
 sin 
2
 θ
 +{ 
2
 
(a 
2
 +b 
2
 )sin 
2
 θ
 }
∴x= 
2
 +b 
2
 
2
 −b 
2
 
  
2
 cos 
2
 θ+a 
2
 sin 
2
 θ
2
 cos 
2
 θ−a 
2
 sin 
2
 θ
 Acosθ....1
and y=−(a 
2
 −b 
2
 ) 
2
 
Asinθ
  
2
 
(a 
2
 +b 
2
 )
 cos 
2
 θ+ 
2
 
(a 
2
 +b 
2
 )
 sin 
2
 θ
1−( 
2
 
2
 +b 
2
 
 )cos 
2
 θ
 
2
 +b 
2
 
2
 −b 
2
 
  
2
 cos 
2
 θ+a 
2
 sin 
2
 θ
2
 cos 
2
 θ−a 
2
 sin 
2
 θ
 Asinθ.....2
y
x
 = 
sinθ
cosθ
 
y
sinθ
 = 
x
cosθ
 = 
2
 +y 
2
 
 
1
 .....3
Eliminating from θ from 1 and 3, we getx= 
2
 +b 
2
 
2
 −b 
2
 
 A 
2
 +y 
2
 
 
x
  
2
 x 
2
 +a 
2
 y 
2
 
2
 x 
2
 −a 
2
 y 
2
 
 
or (a 
2
 +b 
2
 ) 
2
 (x 
2
 +y 
2
 )(b 
2
 x 
2
 +a 
2
 y 
2
 ) 
2
 =(a 
2
 −b 
2
 ) 
2
 (b 
2
 x 
2
 −a 
2
 y 
2
 ) 
2

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