I have been drawing some pictures using tikz, and am wondering if I can name a number.
For example, I pick a point
$A$ with position angle
$\alpha=45\degree$ on a circle, and a line going through that point with direction angle
$\beta=\alpha+90\degree=135\degree$ (wich is perpendicular to the position vector).
Later I change the point
$A$ to be
$\alpha=60\degree$, and then
Now I change both angles manually. If I can name the first angle
$\alpha$ and the second angle
$\beta$, then I only need to change
$\alpha$: $\beta$ will vary accordingly.
Is there a way to do this, naming a number? Thanks!