By Mansi Yadav

Verified by Ajay Kumar

If \(\sec^2\theta+\tan^2\theta=\frac{7}{12}\), find the value of \(\sec^4\theta-\tan^4\theta\).

  1. \(\frac{7}{12}\)

  2. \(\frac{13}{12}\)

  3. 1

  4. \(\frac{5}{12}\)

Answer: A

Solution

Solution: \(\sec^4\theta-\tan^4\theta=(\sec^2\theta-\tan^2\theta)(\sec^2\theta+\tan^2\theta)\). Since \(\sec^2\theta-\tan^2\theta=1\), the expression is \(1\times\frac{7}{12}=\frac{7}{12}\). Trick: Factor the difference of two squares. Source note: The printed condition \(\sec^2\theta+\tan^2\theta=\frac{7}{12}\) is not possible for a real angle, but the green-marked answer is retained.

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