Identify lines of symmetry

Learning Objectives Define symmetry and a line of symmetry. Identify symmetrical and asymmetrical figures. Draw lines of symmetry in common two-dimensional shapes. Determine if a figure has one, multiple, or no lines of symmetry. Recognize lines of symmetry in real-world objects and patterns. Explain that a line of symmetry divides a figure into two congruent (identical) halves. Have you ever folded a piece of paper and cut out a shape, then unfolded it to see a perfect, balanced design? ✂️ That's symmetry in action! In this lesson, we'll explore what makes a shape symmetrical and how to find its 'line of symmetry.' Understanding symmetry helps us see balance and beauty in the world around us, from nature to art and design. Real-World Applications Bu...

TermDefinitionExample SymmetryA figure has symmetry if it can be divided by a line into two identical halves that are mirror images of each other.A butterfly has symmetry because its left wing is a mirror image of its right wing. Line of SymmetryAn imaginary line that divides a figure into two congruent (same size and shape) halves that are exact mirror images of each other.The line down the middle of a heart shape is a line of symmetry. Symmetrical FigureA figure that has at least one line of symmetry.A square is a symmetrical figure because it has four lines of symmetry. Asymmetrical FigureA figure that has no lines of symmetry.A handprint is usually an asymmetrical figure because you cannot fold it to make two identical halves. ReflectionThe transformation that creates a mirror image o...

The Fold Test Rule $ ext{Figure Half}_1 \xrightarrow{\text{Fold along L}} \text{Figure Half}_2 \implies \text{Figure Half}_1 \cong \text{Figure Half}_2$ If you can fold a figure along a line (L) and the two halves match up perfectly, then that line is a line of symmetry. The symbol $\cong$ means 'is congruent to' or 'is identical to'. The Mirror Image Rule $ ext{Figure Half}_1 \xrightarrow{\text{Reflect across L}} \text{Figure Half}_2 \implies \text{Figure Half}_1 \text{ is mirror image of } \text{Figure Half}_2$ A line (L) is a line of symmetry if one half of the figure is the exact mirror image of the other half when reflected across that line. The Congruent Halves Rule $ ext{Figure } \xrightarrow{\text{Divided by L}} (\text{Half}_1, \text{Half}_2...