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Question
Prove the following identity :
`sec^4A - sec^2A = sin^2A/cos^4A`
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Solution
`sec^4A - sec^2A = 1/cos^4A - 1/cos^2A`
= `(1 - cos^2A)/cos^4A`
= `sin^2A/cos^4A` [∵ `sin^2A = 1 - cos^2A`]
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