Sec^4A - Sec^2 A is equal to ? – InterviewSolution

1.	Sec^4A - Sec^2 A is equal to ?
Answer» Since all the options involve the trigonometric ratio tan θ, so we use the identity 1 + tan2θ = sec2θ. To find: sec4A – sec2A Consider sec4A – sec2A = (sec2A)2 – sec2A Now, as sec2A = 1 + tan2A ⇒ sec4A – sec2A = (sec2A)2 – sec2A = (1 + tan2A)2 – (1 + tan2A) = 1 + tan4A + 2 tan2A – 1 – tan2A = tan4A + tan2A Sec^4A-sec^2A =\xa0tan^4A+tan^2

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