📝 Practice Worksheets
🛠️ Related Tools
🔑 Key Concepts
- A reflection flips a figure across a line of reflection.
- Reflecting across the y-axis changes each point from \(x,y\) to \(-x,y\).
- The y-coordinate stays the same when reflecting across the y-axis.
- Reflected points are the same distance from the line of reflection as the original points.
💡 Main Idea
To reflect a figure across the y-axis, keep the y-coordinate the same and change the sign of the x-coordinate. In coordinate rule form, \(x,y\) becomes \(-x,y\). This means points to the left of the y-axis move the same distance to the right of it, and points to the right move the same distance to the left.
📚 What You Should Already Know
Students should already know how to plot ordered pairs on the coordinate plane, identify the x-axis and y-axis, and read coordinates correctly as \(x,y\). Students should also understand that the sign of a coordinate tells whether a point is above or below the x-axis or left or right of the y-axis. In addition, students should know the names and locations of the four quadrants — Quadrant I, Quadrant II, Quadrant III, and Quadrant IV — and understand the sign patterns of coordinates in each quadrant.
🚀 What Comes Next
After learning reflections across the y-axis, students can extend this idea to reflections across the x-axis, reflections across other vertical and horizontal lines, and sequences of transformations that combine reflections, rotations, and translations. These concepts help build a deeper understanding of congruence and geometric transformations on the coordinate plane.
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