ROTATIONAL SYMMETRY
Definition Of Rotational Symmetry
If a figure matches itself a number of times while it is being turned about a point, then it is said to have Rotational Symmetry.
More About Rotational Symmetry
The number of positions a figure can be rotated to, without bringing in any changes to the way it looks originally, is called its order of rotational symmetry.
Video Examples: Geometry - Rotational Symmetry
Example of Rotational Symmetry
The above figure appears to be unchanged even after the figure is rotated. Hence it has rotational symmetry.
Solved Example on Rotational Symmetry
Ques: Which of the letters has rotational symmetry?
Choices:
A. Figure 2
B. Figure 4
C. Figure 3
D. Figure 1
Correct Answer: B
Solution:
Step 1:A figure has a rotational symmetry, if its image, after a rotation of less than 360°, appears exactly the same as that of the original figure.
Step 2:
Step 3: When 'H' is rotated by 180°, it exactly fits on the original figure
Step 4: So, the letter in Figure 4 has a rotational symmetry.
Quick Summary
- Rotational symmetry occurs when a shape looks the same after a rotation.
- The order of rotational symmetry is the number of times a figure looks the same during a full rotation.
🍎 Teacher Insights
Use real-world examples to illustrate rotational symmetry, such as snowflakes or pinwheels. Provide hands-on activities where students can rotate shapes to explore symmetry.🎓 Prerequisites
- Symmetry
- Angles
- Basic geometric shapes
Check Your Knowledge
Q1: Which of the following letters has rotational symmetry?
Q2: A square has rotational symmetry of order:
Frequently Asked Questions
Q: What is the order of rotational symmetry?
A: The order of rotational symmetry is the number of positions a figure can be rotated to, without changing its original appearance.
Q: Does a shape with no symmetry have rotational symmetry?
A: Yes, every shape has rotational symmetry of order 1 (rotating 360 degrees).