On a graph paper plot the triangle ABC whose vertices are at points A(5, 4), B(7, 5) and C(-3, 6). On the same graph, draw the image of the triangle ABC under reflection in the line y = 3. Mark any two points on the graph paper which are invariant under this reflection. Also, write the co-ordinates of points marked.

Let A'B'C' be the image of triangle ABC under the reflection in line y = 3.

From graph,

Coordinates of points A' = (5, 2), B' = (7, 1) and C' = (-3, 0).

We know that,

Any point that lies on a particular line is invariant under reflection in that same line.

Mark point I and J on the line y = 3.

From graph,

Coordinates of points I = (-5, 3) and J = (-2, 3).