1. M6G1b – Investigate rotational symmetry, including degree of rotation.

2. Vocabulary 1) Rotate – to turn a figure around a fixed point
2) Point of rotation - the point around which a figure is rotated (a.k.a. the center of rotation)
3) Rotational Symmetry – when a figure fits exactly on top of itself after a rotation of 180° or less
4) Angle of rotation – the smallest angle a figure can be rotated to look exactly the same

3. A square has rotational symmetry.
The smallest angle a figure can be rotated and still look the same is called the angle of rotation.
What is the angle of rotation of a square?
90°

4. Does a rectangle have rotational symmetry?
What is the degree of rotation?
180°

5. Does each figure have rotational symmetry?
360 ÷ 4 = 90
360 ÷ 3 =
120
360 ÷ 6 = 60
To find the degree of rotation mathematically, divide ______ by the number of times the pattern _________
360°
repeats.

6. Do these figures have rotational symmetry?NO
Yes - 90°
Yes - 45° NO
Yes - 180°
Yes - 72°

7. Rotational Symmetry in the Alphabet
Which letters have rotational symmetry? For those with rotational symmetry, what is the degree of rotation? A B C D E F G H I J
180° K L
180° M N
180° O P
180° Q R S T U V W X Y Z
180°
180°
180°

8. Rotational Symmetry all around us
Which road signs have rotational symmetry?

9. Rotational Symmetry all around us
120°
180°
180°

10. Rotational Symmetry all around us
90°
120°
180°

11. Rotational Symmetry all around us
120°
180°