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प्रश्न
(sec θ + tan θ) . (sec θ – tan θ) = ?
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उत्तर
(sec θ + tan θ)(sec θ – tan θ)
= sec2θ – tan2θ ...[∵ (a + b)(a – b) = a2 – b2]
= 1 ...`[(∵ 1 + tan^2θ = sec^2θ),(∴ sec^2θ - tan^2θ = 1)]`
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