posted by Brandon on .
The coordinates of the vertices of triangle CDE are C(1,4), D(3,6), and E(7,4). If the triangle is reflected over the line y=3, what are the coordinates of the image of D?
I think (3,-6), but not real sure.
think of folding the diagram on the line y=3. x-values don't change, and y-values are moved the same distance from the line y=3.
The distance of (x,y) from (x,3) is y-3.
so, (x,y) --> (x,3-(y-3)) = (x,6-y)
(3,6) --> (3,0)
D is 3 units above the line y=3, so it moves to 3 units below the line, or y=0.
dats correct O: howd you know <3
If triangle ABC is reflected across the y-axis, what are the coordinates of A'?