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.

geometry 
Steve,
think of folding the diagram on the line y=3. xvalues don't change, and yvalues are moved the same distance from the line y=3.
The distance of (x,y) from (x,3) is y3.
so, (x,y) > (x,3(y3)) = (x,6y)
(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. 
geometry 
lulabye,
dats correct O: howd you know <3

geometry 
ensy,
If triangle ABC is reflected across the yaxis, what are the coordinates of A'?