PEAZIT Aha card
Go straight to resources ↓Reflection preserves distance from the mirror line
The segment joining a point to its reflection is perpendicular to the mirror line and bisected by it. Across the y-axis, x changes sign.
| Relation | Meaning |
|---|---|
| P = (3; 2) | The first coordinate measures horizontal displacement. |
| x = 0: P′ = (−3; 2) | Move equally far to the opposite side. |
| d(P, x=0) = d(P′, x=0) = 3 | Perpendicular distance stays unchanged. |
One worked example
- P = (3; 2)The first coordinate measures horizontal displacement.
- x = 0: P′ = (−3; 2)Move equally far to the opposite side.
- d(P, x=0) = d(P′, x=0) = 3Perpendicular distance stays unchanged.
Watch out: Points on the mirror line stay fixed. Reflection across the x-axis changes y's sign instead.
Goal, prerequisites and card origin
What you will learn: Find a point's reflection across an axis.
What you need first: Point coordinates and negative numbers.
An original PEAZIT working card. Independent expert review and effectiveness testing have not yet taken place. · v1
Show connections
The segment joining a point to its reflection is perpendicular to the mirror line and bisected by it. Across the y-axis, x changes sign.