Learning to find Symmetry
Can you identify symmetry in a figure or an image?
Describe what symmetry you see in the image below.
Show the image has symmetry by constructing at least one line of symmetry.
Steps:
1. Plot a pair of points on the image that you think are mirror images of each other.
2. Use the segment tool to connect these points with a straight line. (To make the line stand out, change its style to blue and dashed.)
3. Plot a second pair of points that you think are mirror images of each other.
4. Use the segment tool to connect the first set of points with a straight line. (To make the line stand out, change its style to blue and dashed.)
If the shape has symmetry, the line of reflection would run through the center of the two lines you constructed and would be perpendicular to them.
To construct the line of symmetry follow these steps:
5. Use the midpoint tool to locate the midpoint of the two segments you constructed.
6. Use the line tool (not the segment tool), to construct a line through the two midpoints.
7. To check that this line is perpendicular to your segments, use the angle tool to measure the angle between the proposed line of reflection and each segment. (Do this twice, once for each line. You only need to check one of the 4 angles created by the two intersecting lines.)
If the angle you measure between your segments and the line of reflection is 90 degrees (or very close to it) you have constructed a line of reflection and your shape has symmetry along that line.
