I am learning to use TikZ to draw things in LaTeX. One of the things that TikZ seems to use everywhere for specifying coordinates is a tuple.  For example,

\begin{tikzpicture}
  \node[isosceles triangle, isosceles triangle apex angle=70,
     draw=black,fill=white, inner sep=0pt,anchor=lower 
     side,rotate=90,draw=black,
     fill=white, minimum height=2 cm] (a) at (0,0) {};
\end{tikzpicture}


Creates a small isosceles triangle.  Note the use of (0,0).  Let's encapsulate making a triangle as above with the following macro.

\newcommand\Tri[3]{ 
  \node[isosceles triangle, isosceles triangle apex angle=70,
     draw=black,fill=white, inner sep=0pt,anchor=lower 
     side,rotate=90,draw=black,
     fill=white, minimum height={#2} cm] (#1) at #3 {};}


Suppose I wanted to define a function that takes in a size and starting coordinate, and draws a "triangle" of triangles such as

\begin{tikzpicture}
  \Tri{a}{1}{(-1,0)}
  \Tri{b}{1}{(1,0)}
  \Tri{c}{1}{(0,1.41)}
\end{tikzpicture}


The simple way to do this is to make a macro \TriTri, such that \TriTri{a}{n}{x}{y} creates a triangle of triangles, with bottom triangle anchored at (x,y).

\newcommand\TriTri[4]{ 
  \Tri{#1}{#2}{(#3,#4)}
  \Tri{#1}{#2}{(#3+2*#2,#4)}
  \Tri{#1}{#2}{(#3+#2,{sqrt(2*#2*#2)})}} %% note #3+#2 = (x1 + x2)/2 
                                         %% the sqrt bit is sqrt(size^2 + size^2)
}


I have gotten this to work! But what I would like to do is instead of having x and y input separately, I would like to have them input as a coordinate pair. I would like to reference the coordinates as \first,\second.  So that \first(x,y) = x. The desired effect is that

$$\first(1,2)$$


would be the same as

$$1$$



Question: Grinding sound during cold start?
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