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If \(\tan^2 x = 1 - a^2\), then the value of \(\sec x + \tan^3 x \,\mathrm{cosec}\, x\) is:

This question was previously asked in
RRB Technician 2026 Grade 3 Question Paper (7-Oct-2026) (Shift 3)
The correct answer is

\((2 - a^2)^{\frac{3}{2}}\)

Write \(\tan^3 x \,\mathrm{cosec}\, x = \tan^2 x \cdot \frac{\sin x}{\cos x} \cdot \frac{1}{\sin x} = \tan^2 x \sec x\).

So the expression becomes \(\sec x + \tan^2 x \sec x = \sec x (1 + \tan^2 x)\).

Using \(1 + \tan^2 x = \sec^2 x\), the expression equals \(\sec^3 x = (\sec^2 x)^{\frac{3}{2}} = (1 + \tan^2 x)^{\frac{3}{2}}\).

Substituting \(\tan^2 x = 1 - a^2\): \((1 + 1 - a^2)^{\frac{3}{2}} = (2 - a^2)^{\frac{3}{2}}\).

Hence, the answer is \((2 - a^2)^{\frac{3}{2}}\).

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