SOLUTION: An object that repeats itself every 120 degrees of rotation has rotation symmetry of order: a) 0 b) 1 c) 3 d) 4 and why?

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Question 1150867: An object that repeats itself every 120 degrees of rotation has rotation symmetry of order:
a) 0
b) 1
c) 3
d) 4
and why?

Found 2 solutions by MathLover1, jim_thompson5910:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

An order n+rotation corresponds to a 360%2Fn angle of rotation.
3 rotation (also called 3-fold rotation), and the angle of rotation would be computed by taking 360+and dividing it by 3:
360%2F3=120
so, answer is: c) 3

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Answer: C) 3

This is because there are 360 degrees in a full circle, and 360/120 = 3.

Imagine an equilateral triangle that has one vertex pointing directly north. If we rotate that triangle 120 degrees (clockwise or counterclockwise, it doesnt matter), we get the same exact triangle as before: an equilateral triangle with one vertex pointing directly north.

It might help to cut out an equilateral triangle to place on your desk, then have a friend rotate the triangle as instructed. If you close your eyes during the rotation, then you'll open them to find that nothing has changed. The "before" and "after" triangles are identical.

This process happens exactly 3 times before the angle of rotation gets to 360 (after that point you've done a full revolution and back to square one). So that's one interpretation of what the "3" means. The link below probably does a much better job explaining through a visual approach.

More information
https://www.mathsisfun.com/geometry/symmetry-rotational.html
The page shows various examples of rotational symmetry through really cool animations.