Reflecting Shapes Across Mirror Lines
This animation shows how 2D shapes reflect across mirror lines such as the x-axis, y-axis, and y=x. Each point connects to its image with a perpendicular segment bisected by the mirror line, demonstrating equal distances and reversed orientation. A worked example reflects a triangle in the y-axis, tracking coordinate changes step by step. Useful for IGCSE, GCSE, Edexcel, and O Level students learning coordinate geometry and transformation rules.
Narrated · 16:9 · Preview before teaching · automatic layout checks do not establish subject accuracy
The prompt that made it
Geometrical Transformation: Reflection Audience: IGCSE, gcse, Edexcel, and O level student Teaching plan: Learning goal: Students will identify and perform reflections of 2D shapes in common mirror lines, describe the invariant points and perpendicular distances involved, and verify coordinates accurately. 1. Intuition: A reflection flips a shape across a mirror line. The image is the same size and shape, but orientation reverses; points on the mirror line stay fixed. 2. Visual explanation: Join each point to its image with a segment perpendicular to the mirror line. The mirror line bisects each segment, so both points are equally distant from it. 3. Rules and edge cases: In the coordinate plane, reflect in the x-axis: (x,y)→(x,−y); in the y-axis: (x,y)→(−x,y); in y=x: (x,y)→(y,x). 4. Worked example: Reflect triangle A(1,2), B(4,2), C(1,5) in the y-axis. Plot or calculate A′(−1,2), B′(−4,2), C′(−1,5), then check equal perpendicular distances. 5. Check for understanding: Students reflect a quadrilateral in the x-axis and explain which vertices move, which remain fixed, how distances are preserved, and why the image has reversed orientation.
Make the next one in this series
- Animate rotation of shapes about a fixed point through 90°, 180°, and 270°
- Show enlargement of a shape using a scale factor and centre of enlargement
- Compare translation using column vectors with reflection and rotation on the same shape
