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Some Applications Of Trigonometry

Question
CBSEENMA10007735

Prove the following identities where the angles involved are acute angles for which the expressions are defined.
fraction numerator cosA over denominator 1 plus sinA end fraction plus fraction numerator 1 plus sinA over denominator cosA end fraction equals space 2 space secA.

Solution

L.H.S. = fraction numerator cosA over denominator 1 plus sinA end fraction plus fraction numerator 1 plus sinA over denominator cosA end fraction
equals space fraction numerator cos squared straight A plus left parenthesis 1 plus sinA right parenthesis squared over denominator left parenthesis 1 plus sinA right parenthesis space cos space straight A end fraction
equals space fraction numerator cos squared straight A plus 1 plus sin squared straight A plus 2 space sinA over denominator left parenthesis 1 plus sinA right parenthesis space cosA end fraction
equals space fraction numerator left parenthesis cos squared straight A plus sin squared straight A right parenthesis space plus space 2 space sinA space plus space 1 over denominator left parenthesis 1 plus sinA right parenthesis space cosA end fraction
equals space fraction numerator 1 plus 2 space sinA space plus space 1 over denominator left parenthesis 1 plus sinA right parenthesis space cosA end fraction space equals space fraction numerator 2 plus 2 space sinA over denominator left parenthesis 1 plus sinA right parenthesis space cosA end fraction
equals space fraction numerator 2 space left parenthesis 1 plus sin space straight A right parenthesis over denominator left parenthesis 1 plus sin space straight A right parenthesis space cos space straight A end fraction equals 2 over cosA
equals space 2 space sec space straight A space equals space straight R. straight H. straight S.
Hence comma space straight L. straight H. straight S. space equals space straight R. straight H. straight S.

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