{{ toc.name }}
{{ toc.signature }}
{{ toc.name }} {{ 'ml-btn-view-details' | message }}
{{ stepNode.name }}
Proceed to next lesson
Lesson
Exercises
Recommended
Tests
An error ocurred, try again later!
Chapter {{ article.chapter.number }}
{{ article.number }}. 

{{ article.displayTitle }}

{{ article.introSlideInfo.summary }}
{{ 'ml-btn-show-less' | message }} {{ 'ml-btn-show-more' | message }} expand_more
{{ 'ml-heading-abilities-covered' | message }}
{{ ability.description }}

{{ 'ml-heading-lesson-settings' | message }}

{{ 'ml-lesson-show-solutions' | message }}
{{ 'ml-lesson-show-hints' | message }}
{{ 'ml-lesson-number-slides' | message : article.introSlideInfo.bblockCount}}
{{ 'ml-lesson-number-exercises' | message : article.introSlideInfo.exerciseCount}}
{{ 'ml-lesson-time-estimation' | message }}

Concept

Line Symmetry

A figure in the plane has line symmetry if the figure can be mapped onto itself by a reflection in a line. This line of reflection is called the line of symmetry. When a figure has line symmetry, it is said to be reflectionally symmetric or line symmetric.
An isosceles triangle with its line of symmetry
Some figures can have more than one line of symmetry. For example, a square has four — the lines passing thought the midpoints of opposite sides and the lines containing the diagonals of the square.
A square and its four lines of symmetry