Correct answer: |a| ≤ 1/√2
The equation sin⁻¹x = 2 sin⁻¹a requires that the values of sin⁻¹a must be within the range of the arcsine function, which is defined for inputs between -1 and 1. The maximum value of 2 sin⁻¹a occurs when |a| is at most 1/√2, ensuring that the output remains within the valid range of the arcsine function.