Reflecting a shape across a line
A reflection is a flip over a line, called the line of reflection. Every point of the original shape lands on the other side of the line at the same perpendicular distance.
Method
- Pick a vertex of the shape.
- Draw or imagine a line perpendicular to the mirror line through that vertex.
- Measure the distance from the vertex to the line of reflection.
- Mark the reflected point on the same perpendicular line, the same distance on the opposite side.
- Repeat for each vertex.
- Connect the new points in the same order to form the reflected shape.
Useful idea
If a point lies on the line of reflection, it stays in the same place. If the line is vertical or horizontal, it can help to count units directly; for slanted lines, use perpendicular distances carefully.
Check your answer
- Each image point should be the same distance from the line as its original point.
- The reflected shape should be the same size and shape, only flipped.
- If you reflect the result again across the same line, you should get the original shape back.