Q.Find the minimum value of \(9 \tan^2 \theta + 4 \cot^2 \theta\).

Let’s consider: \[ 9 \tan^2 \theta + 4 \cot^2 \theta \] We rewrite it as: \[ = (3 \tan^2 \theta - 2 \cot^2 \theta)^2 + 2 \cdot 3 \tan \theta \cdot 2 \cot \theta \] \[ = (3 \tan^2 \theta - 2 \cot^2 \theta)^2 + 12 \] Since squares are always non-negative: \[ \ge 12 \] Therefore, the minimum value of \(9 \tan^2 \theta + 4 \cot^2 \theta\) is 12.
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