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Question
(sec θ + tan θ) . (sec θ – tan θ) = ?
Solution
(sec θ + tan θ)(sec θ – tan θ)
= sec2θ – tan2θ ......[∵ (a + b)(a – b) = a2 – b2]
= 1 ......`[(because 1 + tan^2theta = sec^2theta),(therefore sec^2theta - tan^2theta = 1)]`
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