Solve `(x^2-4)sqrt(x^2 -1) lt 0.`

Explanation

To solve the inequality \((x^2 - 4) \sqrt{x^2 - 1} < 0\), we will follow these steps:

### Step 1: Analyze the square root term
The term \(\sqrt{x^2 - 1}\) must be defined and positive. Therefore, we need:
\[ x^2 - 1 \geq 0 \]
This simplifies to:
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