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Question
Prove that identity:
`(sec A - 1)/(sec A + 1) = (1 - cos A)/(1 + cos A)`
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Solution
LHS = `(sec A - 1)/(sec A + 1)`
= `(1/cos A - 1)/(1/cos A + 1)`
= `((1 - cos A)/cos A)/((1 + cos A)/cos A)`
= `(1 - cos A)/(1 + cos A)`
= RHS
Hence proved.
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