দেখাই যে : \(cosec^2 48°– \tan^2 42°=1\)


\(cosec ^2 48°-tan^2⁡ 42° \)
\(=cosec^2 (90°-42°)-tan^2⁡ 42° \)
\(=sec^2⁡ 42° -tan^2⁡ 42° [∵cosec (90°-θ)=sec⁡θ] \)
\(=1\) (প্রমাণিত) \( [∵sec^2⁡θ-tan^2⁡θ=1 ]\)

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