The apothem is 3√3 units because it is .

In the right triangle formed by the apothem, half a side, and a radius, the angles are 30°, 60°, and 90°. The apothem is the side opposite the 60° angle, so it is √3 times the shorter side. If half the side is 3 units, the apothem is 3√3 units.

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