#184: Matrix Transform explain

[A square matrix next to a vertical two-by-one matrix, equated to a horizontal matrix that looks like the two-by-one matrix turned 90 degrees.]

[Square matrix:

cos90° sin90°

-sin90° cos90°]

[Two by one matrix:]

[a₁

a₂]

[An equal sign]

[The same two by one matrix, but rotated by 90 degrees clockwise:]

[a₁

a₂]