Step-by-step explanation:
We have,
[tex]\begin{gathered} \bullet \: \bold{ - \dfrac{\pi}{4} < \beta < 0 < \alpha < \dfrac{\pi}{4} } \\ \\ \implies \: - \dfrac{\pi}{4} < \alpha + \beta < \dfrac{\pi}{4} \end{gathered}[/tex]
[tex]\begin{gathered} \rm\bullet \: \: \: \sin( \alpha + \beta ) = \dfrac{1}{3} \: \: \: \: \: and \: \: \: \: \: \cos( \alpha - \beta ) = \dfrac{2}{3} \\ \end{gathered} [/tex]
Now,
[tex]\begin{gathered} y= \bigg( \dfrac{ \sin( \alpha ) }{ \cos( \beta ) } + \dfrac{ \cos( \beta ) }{ \sin( \alpha ) } + \dfrac{ \cos( \alpha ) }{ \sin( \beta ) } + \dfrac{ \sin( \beta ) }{ \cos( \alpha ) } \bigg)^{2} \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \bigg( \dfrac{ \sin( \alpha ) }{ \cos( \beta ) } + \dfrac{ \sin( \beta ) }{ \cos( \alpha ) } + \dfrac{ \cos( \beta ) }{ \sin( \alpha ) } + \dfrac{ \cos( \alpha ) }{ \sin( \beta ) } \bigg)^{2} \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \bigg( \dfrac{ \sin( \alpha ) \cos( \alpha ) + \sin( \beta \cos( \beta ) ) }{ \cos( \beta ) \cos( \alpha) } + \dfrac{ \sin( \alpha) \cos( \alpha ) + \sin( \beta ) \cos( \beta ) }{ \sin( \alpha ) \sin( \beta ) } \bigg)^{2} \\\end{gathered}[/tex]
[tex]\begin{gathered} \implies y= \bigg( \dfrac{ \sin( \alpha + \beta ) }{ \cos( \beta ) \cos( \alpha) } + \dfrac{ \sin( \alpha + \beta ) }{ \sin( \alpha ) \sin( \beta ) } \bigg)^{2} \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \sin^{2} ( \alpha + \beta ) \bigg( \dfrac{ 1 }{ \cos( \beta ) \cos( \alpha) } + \dfrac{ 1 }{ \sin( \alpha ) \sin( \beta ) } \bigg)^{2} \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \sin^{2} ( \alpha + \beta ) \bigg( \dfrac{\cos( \beta ) \cos( \alpha) + \sin( \alpha ) \sin( \beta ) }{ \cos( \beta ) \cos( \alpha) \sin( \alpha ) \sin( \beta )} \bigg)^{2} \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \sin^{2} ( \alpha + \beta ) \bigg( \dfrac{\cos( \alpha - \beta ) }{ \cos( \beta ) \cos( \alpha) \sin( \alpha ) \sin( \beta )} \bigg)^{2} \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \dfrac{4\sin^{2} ( \alpha + \beta ) \cdot\cos^{2} ( \alpha - \beta ) }{ \left \{2\cos( \alpha ) \cos( \beta ) \cdot 2\sin( \alpha ) \sin( \beta ) \right \}^{2} } \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \dfrac{4\sin^{2} ( \alpha + \beta ) \cdot\cos^{2} ( \alpha - \beta ) }{ \left \{\cos( \alpha + \beta ) + \cos( \alpha + \beta ) \right \} ^{2} \left \{ \cos( \alpha - \beta ) - \cos( \alpha + \beta ) \right \}^{2} } \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \dfrac{4\sin^{2} ( \alpha + \beta ) \cdot\cos^{2} ( \alpha - \beta ) }{ \left \{ \cos^{2} ( \alpha - \beta ) - \cos^{2} ( \alpha + \beta ) \right \}^{2} } \\\end{gathered}[/tex]
[tex]\begin{gathered} \implies y= \dfrac{4\sin^{2} ( \alpha + \beta ) \cdot\cos^{2} ( \alpha - \beta ) }{ \left \{ \cos^{2} ( \alpha - \beta ) - 1 + \sin^{2} ( \alpha + \beta ) \right \}^{2} } \\\end{gathered}[/tex]
Putting the values given above, we get,
[tex]\begin{gathered} \implies y= \dfrac{4 \cdot \dfrac{1}{9} \cdot\dfrac{4}{9} }{ \left \{ \dfrac{4}{9} - 1 + \dfrac{1}{9} \right \}^{2} } \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \dfrac{\dfrac{16}{81} }{ \left \{ \dfrac{5}{9} - 1\right \}^{2} } \\\end{gathered}[/tex]
[tex]\begin{gathered} \implies y= \dfrac{\dfrac{16}{81} }{ \left \{ \dfrac{5 - 9}{9}\right \}^{2} } \\\end{gathered} [/tex]
[tex]\begin{gathered} \implies y= \dfrac{\dfrac{16}{81} }{ \left \{ \dfrac{- 4}{9}\right \}^{2} } \\\end{gathered}[/tex]
[tex]\begin{gathered} \implies y= \dfrac{\dfrac{16}{81} }{ \dfrac{16}{81}} \\\end{gathered} [/tex]
[tex]⟹y=1[/tex]