Posted by robert on Saturday, December 1, 2007 at 10:49pm.
After a triangle is rotated 180 degrees, its vertices are at (4,1),(1,4), and (5,8). What were the coordinates of the vertices before the rotation?
I think the answer is (1,4), (4,1),(8,5). In rotation, the coordinates get switched. All I just did was switch the numbers and signs. Is this right?

math  Reiny, Saturday, December 1, 2007 at 11:59pm
do you want your rotation about the origin?
If so, then the line joining a point and its image point should pass through the origin, yours don't.
if you interchange the x and y coordinates you are forming a reflection in the line y=x
try switching the signs only and plotting the points.
You should have tried plotting right away.