A-Level Further Maths: C3-21 3D Matrices: Rotation of 90 degrees anticlockwise about the x-axis

[nosir]

Do we ever get asked to find rotations or reflections (or any other transformation for that matter) about certain planes, rather than just simply an axis?
What would a rotation of 90 degrees anticlockwise of the XY plane even look like?

[joshplayz]

What happens if i defined my x axis to be in the other direction, since it seems completely arbitrary to pick a certain direction?

[newton]

Will you make videos on inverse transformations & matrix algebra

[wetter]

See it's funny because I'm trying to figure this problem out exactly in the scope of aviation.
Imagine a plane sliding in for landing. He's gliding in on a line. now picture you're looking down that line, that perfect line.

Now that graph's axis you're looking down that's in 3d....is now a 2d graph with an x and a y axis. And every time that pilot deviates from that perfect line, it creates two distances...an X distance and a Y distance. Unfortunately, I'm stuck trying to represent those graphs in a uniform manner such that I can calculate X and Y in 2d