PROFESSOR: One important piece of advice.
Always, I stress always, use what we call a right-handed
coordinate system.
And a right-handed coordinate system is defined in the
following way.
That x roof crossed with y roof equals z roof.
In other words, this positive x direction, positive y
direction, positive z direction, this is a
right-handed coordinate system.
because the unit vector in the x direction, x roof, if I
cross that with the unit vector in the y direction, I
get this vector.
A left-handed coordinate system, which would be a
dreadful thing to use because you can get yourself
into very hot water.
A left-handed would be this.
y, x, z.
Now you would have that x roof cross y roof
would be minus z roof.
You never, ever do that, never.
You can only get yourself into trouble.