Question 951864
{{{drawing(300,480,-9,1,-9,7,
grid(1),circle(0,0,0.18),locate(0.18,0.5,A),
line(0,0,-8.5,3),
line(-8.5,3,0,6),
line(0,0,0,6),
circle(-8.5,3,0.2),locate(-8.45,3.8,B),
circle(0,6,0.2),locate(0.15,6.5,C),
green(line(0,0,-3,-8.5)),
green(line(-3,-8.5,-6,0)),
green(line(0,0,-6,0)),green(circle(0,0,0.25)),
green(circle(-3,-8.5,0.2)),locate(-2.88,-8.5,green(X)),
green(circle(-6,0,0.2)),locate(-6.5,0,green(Y))
)}}} The transformation rotated everything around the origin by {{{90^o}}} counterclockwise.
Every point stays the same distance from the origin, but in a different direction.
Point (a,0) turns into point (0,a);
point (0,b) turns into point (-b,0), and (adding them up)
point (a,b) turns into point (-b,a):
(0,0) ---> (-0,0) = (0,0)
(-8.5,3) ---> (-3,-8.5)
(0,6) ---> (-6,0)