A-Level Further Maths: C3-07 Matrices: Rotations

[kakashi]

Thanks for these videos, they're 10/10. Very neatly structured & filmed and organised, articulated, designed, presented & explained & clearly delivered. The videos are concise & logical.

[moodymonstrosity]

I have a question, the rotation 180 degree matrix is similar to reflection about y= -x matrix in the previous video, so how do we distinguish? Does it have the same effect?

[JJFHNREHJEDK]

How do you know which to coordinate to write first? As i did (0, 1) then (1, 0) which gave the matrix
( -1 0 )
( 0 1 )
But that's a reflection in y-axis not rotation 90˚ anticlockwise, so how do you know to write them in the other order?