Question

If an object maps onto itself after being rotated 180 degrees or less about a line, it has

Answer 1

rotational symmetry

Explanation:

If an object maps onto itself after being rotated 180 degrees or less about a line, it has rotational symmetry.

Answer 2

rotational symmetry

Explanation:

That's the definition of rotational symmetry: the object maps to itself after rotation of less than one full turn.

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The number of different rotational angles at which the object maps to itself defines the order of the rotational symmetry.