So far, you've learned that reflective symmetry is like having halves that mirror each other.
In this lesson, we're going to explore another type of symmetry that is called rotational symmetry.
Rotational symmetry is a property that a shape has when it still looks the same even when rotated by a partial turn.
Tip: Partial turn is made by turning the shape any degree that is less than 360°.
Look at this square.
What happens if we rotate it a quarter of a turn clockwise?
Tip: A quarter of a turn is 90 degrees.
We get a square that looks like the square that we started with.
Let's try to make another quarter turn.
We still get a square that matches the original.
Let's try to rotate it one more time.
Again, after rotating the square by 90 degrees, the size and shape of the square did not change.
This means that the square's degree of rotation is 90°. ✅
Whether we rotate 90° clockwise or counterclockwise, the size and shape of this square remains the same.
The center is the point where an object rotates.
The square has rotational symmetry.
Let's try rotating this heart 180 degrees clockwise.
Tip: 180 degrees is half a turn.
Did we get a shape that matches the heart that we started with?
No, we didn't.
Let's try turning it 180 degrees counterclockwise instead. Maybe that will show us symmetry:
Nope.
Maybe we can try a different angle. 🤔
We can turn it 90 degrees clockwise.
We still don't get symmetry.
This means that the heart shape does not have rotational symmetry. ❎
We can get any shape to match its original if we make a full turn.
A full turn is 360 degrees.
But a shape has rotational symmetry only if the angle is less than 360 degrees.
Great job learning about rotational symmetry.
Now, try the practice.