REFLECTION-AND-LINE-SYMMETRY

Learning Competency

  • Target code: CMFM11-Q1A2

  • By the end of the lesson, learners should be able to identify five symmetry–related ideas in both nature and art:

    • Reflection symmetry

    • Rotational symmetry

    • Line of symmetry

    • Center of rotation

    • Angle of rotation

Learning Objectives

  • Define symmetry and name its types.

  • Recognize reflection symmetry and line symmetry in real-world objects, artworks, and natural patterns.

  • Perform and document a paper-folding / mirror activity that demonstrates reflection symmetry.

Warm-Up Question

  • “What patterns in nature did you see today that show balance?”

    • Encourages observation of leaves, butterflies, flowers, animal bodies, snowflakes, etc., for evidence of symmetry.

Key Concept: Symmetry

  • Symmetry occurs when something is the same on both sides of a reference division.

  • Visualized by imagining a mirror placed in the center of the figure: whatever appears on one side appears identically on the other.

  • Provides a sense of balance and harmony in design, art, and natural forms.

Reflection Symmetry (Mirror Symmetry)

  • Definition: One half of an object is the mirror image of the other half.

  • Requires a distinct dividing line so that every point on one side maps exactly to a corresponding point on the opposite side.

Mirror / Reflection Analogy

  • Think of holding a physical mirror at the dividing line; the reflection completes the other half perfectly.

Line of Symmetry

  • Also called the mirror line.

  • An imaginary line that cuts a figure into two matching parts that are exact mirror images.

  • A single figure may possess zero, one, or multiple lines of symmetry.

Types of Line Orientation

  • Vertical line: Runs up and down; parallel to the direction of gravity or a straight tree trunk.

  • Horizontal line: Runs left to right; parallel to the horizon or a calm water line.

  • Diagonal line: Slanted; connects points that are not directly above/below or left/right of each other.

Number of Lines of Symmetry (Conceptual Table)

  • Examples (implied though not explicitly shown in slides):

    • 1 line: Heart, human body (front view), most uppercase letters (e.g., A).

    • 2 lines: Rectangle, isosceles trapezoid (if symmetric both vertically and horizontally).