Question
Eliminate $\theta$ from given equations.
$ x=a \cot \theta-b \operatorname{cosec} \theta$
$y=a \cot \theta+b \operatorname{cosec} \theta $

Answer

$ x=a \cot \theta-b \operatorname{cosec} \theta........1$
$y=a \cot \theta+b \operatorname{cosec} \theta........2 $
Adding equations (I) and (II).
$ x+y=2 a \cot \theta$
$\therefore \cot \theta=\frac{x+y}{2 a} $
Subtracting equation (II) from (I),
$ y-x=2 b \operatorname{cosec} \theta$
$\therefore \operatorname{cosec} \theta=\frac{y-x}{2 b} $
Now, $\operatorname{cosec}^2 \theta-\cot ^2 \theta=1$
$ \therefore\left(\frac{y-x}{2 b}\right)^2-\left(\frac{y+x}{2 a}\right)^2=1$
$\therefore \frac{(y-x)^2}{4 b^2}-\frac{(y+x)^2}{4 a^2}=1$
$\text { or }\left(\frac{y-x}{b}\right)^2-\left(\frac{y+x}{a}\right)^2=4 $

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