Maths-
General
Easy
Question
PQ and QR are two focal chords of an ellipse and the eccentric angles of P,Q,R and
, respectively then tan tan is equal to -
- cot
- cot2
- 2 cot
- None of these
The correct answer is: cot2
P (a cos 2 , b sin 2 ), Q (a cos 2 , b sin 2 )
R (a cos 2 , b sin 2 )
chord's PQ equation
cos ( + ) + sin ( + ) = cos ( – )
PQ passes through the focus (ae, 0)
e =
PR passes through the focus (– ae, 0) the
– e =
= –
Apply componendo and dividendo, we get
=
=
tan tan = cot2
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