I'm beginning to use TikZ and am having some issues understanding the proper way to reference my data points without specifying the precise absolute positions for all of them. An example of the simple situation I'm confused with is as follows:
Let's say I have 3 points,
C=(bx,by-1). I want to draw lines between these points, but I also want them to be labelled A, B and C so that I may refer to them later. If I simply define my points A and B like so:
\coordinate (A) at (ax,ay); \coordinate (B) at (bx,by);
then what is the best way to get C? Should I try something like
\coordinate (C) at "some way of referring to B's coordinates and doing math on them"
or do I have to use some (seemingly) clumsy statement like
\coordinate (C) at let \p1 = (B) in (\x1,\y1-1);
It seems like it'd be best if I could do the former option, but many answers on this type of topic online focus on the use of the 'let' command. However, my usage of the let command above is incorrect. I also tried things like
let \p1 =(B) in \coordinate (C) at (\x1,\y1-1);
but this also didn't work. I haven't seen any examples of the let command used in conjunction with \coordinate so not sure what the syntax should be.
So my question is, what is the best way to assign C? I could define it inline when using \draw to draw the line from A to B to C, but then I don't think I'd have access to the C coordinate again without recomputing.