Q.If \(\cos^4\theta - \sin^4\theta = \frac{2}{3}\), then what is the value of \(1 - 2\sin^2\theta\)?

\(\cos^4\theta - \sin^4\theta = \frac{2}{3}\) Or, \((\cos^2\theta)^2 - (\sin^2\theta)^2 = \frac{2}{3}\) Or, \((\cos^2\theta + \sin^2\theta)(\cos^2\theta - \sin^2\theta) = \frac{2}{3}\) Or, \(\cos^2\theta - \sin^2\theta = \frac{2}{3}\) [Because \(\sin^2\theta + \cos^2\theta = 1\)] Or, \(1 - \sin^2\theta - \sin^2\theta = \frac{2}{3}\) Or, \(1 - 2\sin^2\theta = \frac{2}{3}\) (Answer)
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