Q.What is the value of \( \sec^2 12^\circ - \frac{1}{\tan^2 78^\circ} \)? (a) 0 (b) 1 (c) -1 (d) 2
Answer: B
\(\sec^2 12^\circ - \frac{1}{\tan^2 78^\circ}\) \(= \sec^2 12^\circ - \frac{1}{\tan^2(90^\circ - 12^\circ)}\) \(= \sec^2 12^\circ - \frac{1}{\cot^2 12^\circ}\) \(= \sec^2 12^\circ - \tan^2 12^\circ\) \(= 1\)
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