$ = x\left( { - {x^2} - 1} \right) - \sin \theta \left( { - x\sin \theta - \cos \theta } \right) + \cos \theta \left( { - \sin \theta + x\cos \theta } \right)$
$ \Rightarrow - {x^3}$
${\Delta _2} = \left| {\begin{array}{*{20}{c}}
x&{\sin 2\theta }&{\cos 2\theta }\\
{ - \sin 2\theta }&{ - x}&1\\
{\cos 2\theta }&1&x
\end{array}} \right|$
$ \Rightarrow - {x^3}$
${\Delta _1} + {\Delta _2} = - 2{x^3}$
$ x+(\sqrt{2} \sin \alpha) y+(\sqrt{2} \cos \alpha) z=0 $
$ x+(\cos \alpha) y+(\sin \alpha) z=0 $
$ x+(\sin \alpha) y-(\cos \alpha) z=0$
ને એક અસામાન્ય ઉકેલ હોય, તો $\alpha \in\left(0, \frac{\pi}{2}\right)$ બરાબર ............ છે.