Answer: C
\(\sin^2A + \sin^4A = 1\) So, \(\sin^4A = 1 - \sin^2A\) That means, \(\sin^4A = \cos^2A\) Now, \(\cfrac{\sin^4A}{\cos^4A} = \cfrac{\cos^2A}{\cos^4A}\) So, \(\tan^4A = \cfrac{1}{\cos^2A} = \sec^2A\) \(\therefore \tan^2A - \tan^4A\) \(= \tan^2A - \sec^2A\) \(= -(\sec^2A - \tan^2A) = -1\)
\(\sin^2A + \sin^4A = 1\) So, \(\sin^4A = 1 - \sin^2A\) That means, \(\sin^4A = \cos^2A\) Now, \(\cfrac{\sin^4A}{\cos^4A} = \cfrac{\cos^2A}{\cos^4A}\) So, \(\tan^4A = \cfrac{1}{\cos^2A} = \sec^2A\) \(\therefore \tan^2A - \tan^4A\) \(= \tan^2A - \sec^2A\) \(= -(\sec^2A - \tan^2A) = -1\)