⌈1  0⌉⌈x⌉=⌈ x⌉
⌊0 -1⌋⌊y⌋=⌊-y⌋

The above 2x2 matrix reflects a point over the x-axis. (x,y)→(x,-y).

Derive a matrix that will reflect a point over the line y=kx.

[cos(2*atan(k))   sin(2*atan(k))]  
[sin(2*atan(k))  -cos(2*atan(k))]  

Ref(theta) = [cos 2*theta   sin 2*theta]
             [sin 2*theta  -cos 2*theta]

But, Jer, I couldn't find anywhere, the codes for the partial square brackets, sometimes used for floor and ceiling.

PS: Well I now found the codes, but they don't seem to be recognized in the "View Source" view, when going back to the regular view. (&bracketlefttp; etc.)

Edited on April 1, 2015, 4:18 pm

Posted by Charlie on 2015-04-01 16:10:17