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Line of Symmetry

Definition of Line of Symmetry

• Line of symmetry is a line that divides a figure into two congruent parts, each of which is the mirror image of the other.
• When the figure having a line of symmetry is folded along the line of symmetry, the two parts should coincide.

Examples of Line of Symmetry

• The dotted line shown in the figure is the Line of Symmetry.

Solved Example on Line of Symmetry

• Among the dotted lines in the figures, which one is a line of symmetry?

Choices:

A. the dotted lines in Figure 2

B. the dotted lines in Figure 3

C. the dotted lines in Figure 1

D. the dotted lines in Figure 4

Solution:

Step 1: Line of Symmetry is a line that divides the figure into two parts, which are mirror images of each other.

Step 2: Among the choices, the dotted line through the letter M divides it into two parts, which are mirror images of each other.

Step 3: The lines passing through the letters L, P, and Q do not divide them into two parts that would be mirror images of each other.

Step 4: So, the dotted line through the letter M is a line of symmetry.

Related Terms for Line of Symmetry

• Congruent
• Mirror Image
• Symmetry
• Line