If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Lesson 6: Line of symmetry

Symmetry review

Review symmetrical shapes and lines of symmetry.  Then, try some practice problems.

Line of symmetry

A start color #1fab54, start text, l, i, n, e, space, o, f, space, s, y, m, m, e, t, r, y, end text, end color #1fab54 is a line where we can fold the image and have both halves match exactly.
Example:
When we divide the figure with Line start color #1fab54, A, end color #1fab54, the resulting two parts are mirror images of each other:
An isosceles triangle with a line labeled A that passes through the vertex joining the equal length sides to the center of the third side.
Line start color #1fab54, A, end color #1fab54 is a line of symmetry.

Symmetrical figures

Shapes are start color #aa87ff, start text, s, y, m, m, e, t, r, i, c, a, l, end text, end color #aa87ff if they have at least one start color #1fab54, start text, l, i, n, e, space, o, f, space, s, y, m, m, e, t, r, y, end text, end color #1fab54 on them.
Example:
This shape is start color #aa87ff, start text, s, y, m, m, e, t, r, i, c, a, l, end text, end color #aa87ff:
A shape with five sides of equal lengths and all equal angles.
Because we can draw at least one start color #1fab54, start text, l, i, n, e, space, o, f, space, s, y, m, m, e, t, r, y, end text, end color #1fab54 on it:
The same five-sided shape with five lines of symmetry, each cutting it in half through the center point.

Practice

Problem 1
• Current
In the figure below, which of the following is a line of symmetry?
A four-sided shape where the left and right vertical sides are parallel, but the top and bottom sides are not parallel. The right side is longer than the left side. The top side moves up and to the right while the bottom side moves down and to the right. The shape is divided by three lines labeled A, B, and C. Line A is a horizontal line that divides the top and bottom half evenly so when folded, the top and bottom sides match. Line B divides the left and right half evenly, but when folded, both sides do not match. Line C passes through the top left corner and bottom right corner, but is not evenly divided.

Want to join the conversation?

• How many lines of symmetry does a circle have
• Circles have an infinite amount of lines of symmetry. You can go on and on and on and never find a specific number of lines of symmetry. Circles are the only figures that have an infinite amount of lines of symmetry.
• how many lines of symmetry does a circle have
• A circle has infinite lines of symmetry
• how to find total number of lines of symmetry
• just do it as many times and many ways till you get all you need
• I did not understand how the pentagon had symmetry that way can you help me please?
• Yes, if you fold the pentagon over the dotted line, then the two pieces would match perfectly.
• so the amount of sides there is in the shape is how much lines of symmetry there is in that shape
• Symmetry is basically two sides of a shape that are the same. Imagine a triangle split in half. That would be symmetrical. Good luck and keep practicing!
• How many line of symmetry does a circle have?
• A circle has infinite amount of lines maybe 20 or more
• how do you solve decomposing angles when there is no sign of solving it. it is impossible when you have to subtract the numbers and then the answer is wrong, i never get the decomposing angle questions right, i always get 0% in them. geometry is difficult. isn't it. i always try to solve the questions if they are not right, but it never is right and i never get them right even after having a second go at them.
• Every body can make mistakes just keep trying