Now, let’s get ironic for a second. If you draw a line through a circle that doesn’t hit the exact center, you get two pieces. One is a big, chubby crescent, and the other is a skinny little crescent. They are not mirror images.
That’s why Maya was mad at my pizza slicing. I was cutting off-center, giving her one greasy chunk and one half-baked piece of crust. A line of symmetry is a strict boss: it demands the line go through the bullseye.
And don’t even get me started on the “lines” people scribble on paper. If you draw a wobbly squiggle through a circle and call it symmetry, the math gods will personally come and untie your shoelaces. The line has to be straight and through the center. No wiggle room.
What About the Edge?
Here’s a fun detail your geometry teacher probably mumbled too quickly. Every line of symmetry in a circle is technically a diameter. That’s just a fancy word for a line that goes from one side, through the middle, to the other side.
So feel free to impress your friends at a party. “Did you know a circle has as many diameters as it has lines of symmetry? Yeah, it’s infinite. No, you can’t count them. Yes, I am fun at parties.”
Lines Of Symmetry For A Circle at Hamish Riddoch blog
And because the circle is perfectly round at every single point, the reflection never gets distorted. Cut an egg in half and you’ll get a mess. Cut a circle in half, and you get two perfect half-circles. Always.
