alt Hacker News> If you want to rotate things there are usually better ways.
Can you elaborate? If you want a representation of 2D rotations for pen-and-paper or computer calculations, unit complex numbers are to my knowledge the most common and convenient one.
> If you want to rotate things there are usually better ways.
Can you elaborate? If you want a representation of 2D rotations for pen-and-paper or computer calculations, unit complex numbers are to my knowledge the most common and convenient one.
For pen and paper you can hold tracing paper at an angle. Use a protractor to measure the angle. That's easier than any calculation. Or get a transparent coordinate grid, literally rotate the coordinate system and read off your new coordinates.
For computers, you could use a complex number since it's effectively a cache of sin(a) and cos(a), but you often want general affine transformations and not just rotations, so you use a matrix instead.