What you’ll learn
Understand reflections.
Key idea
An axis reflection reverses the perpendicular coordinate but leaves the parallel coordinate unchanged.
Reverse only the perpendicular coordinate; the coordinate parallel to the mirror stays fixed.
Worked example
Classify examples and non-examples for the concept 'Understand reflections'.
Reflect (-2,-2) across the y-axis. Classify proposed image (-2, 2) with coordinate evidence.
- Reflection across the y-axis leaves the parallel coordinate unchanged and reverses the perpendicular coordinate.
- Thus (-2,-2) maps to (2, -2), and (2, 2) maps to (-2, 2); distances to the mirror match on opposite sides.
Answer: False — the perpendicular coordinate changes sign and the actual image is (2, -2).
Quick Check
Classify examples and non-examples for the concept 'Understand reflections'.
Reflect (1,-1) across the x-axis. Classify proposed image (1, 1) with coordinate evidence.