Find the values of x for which expression `sqrt(1-sqrt(1-sqrt(1-x^(2))))` is meaningful.

Explanation

To find the values of \( x \) for which the expression \( \sqrt{1 - \sqrt{1 - \sqrt{1 - x^2}}} \) is meaningful, we need to ensure that all the square roots in the expression are defined and non-negative.

### Step 1: Ensure the innermost square root is defined
The innermost expression is \( \sqrt{1 - x^2} \). For this to be meaningful, we need:
\[ 1 - x^2 \geq 0 \]
This simplifies to:
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