Q.If \( 3x = \csc \alpha \) and \( \cfrac{3}{x} = \cot \alpha \), then find the value of \( 3\left(x^2-\cfrac{1}{x^2}\right) \). (a) \(\cfrac{1}{27}\) (b) \(\cfrac{1}{81}\) (c) \(\cfrac{1}{3}\) (d) \(\cfrac{1}{9}\)
Answer: C
\(3x+ \cfrac{3}{x}=\csc\alpha+\cot\alpha \)
Or, \(3\left(x+\cfrac{1}{x}\right)=\csc\alpha+\cot\alpha\)

Again, \(3x-\cfrac{3}{x}=\csc\alpha-\cot\alpha \)
Or, \(3(x-\cfrac{1}{x})=\csc\alpha-\cot\alpha\)

∴ \(3(x+\cfrac{1}{x})\times 3(x-\cfrac{1}{x})\)
\(=(\csc\alpha+\cot\alpha )(\csc\alpha-\cot\alpha)\)
Or, \(3\times 3\left(x^2-\cfrac{1}{x^2} \right)=\csc^2 \alpha-\cot^2⁡\alpha\)
Or, \(3\times 3\left(x^2-\cfrac{1}{x^2}\right)=1\)
Or, \(3\left(x^2-\cfrac{1}{x^2}\right)=\cfrac{1}{3}\)
(Answer)
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