Tikz example

Suppose you want to draw a diagram like this.

package to be used

\usepackage{tikz}
\usetikzlibrary{intersections, calc, arrows}

I drew the code for two blacked-out triangles side by side.
CALC was used for the calculations.

command definition

I created a command to draw a triangle. I define the coordinates, define the relationship between the coordinates, and then paint it with a fill.

\newcommand{\myTriangle}[1]{
\coordinate (myA) at ($#1+(0,0)$);
\coordinate (myB) at ($#1+(1,1)$);
\coordinate (myC) at ($#1+(2,0)$);
\fill (myA)--(myB)--(myC)--cycle;}

Tikz body

I draw various instructions in the begin and end of the tikzpicture.

\begin{tikzpicture}
...
\end{tikzpicture}

Defining vectors

Define a vector and define a triangle as a place by adding the vectors

\coordinate (R) at (2,0);
\coordinate (U) at (0,1);
\coordinate (LD) at (-1,-1);
\coordinate (RD) at (1,-1);

\coordinate (A) at (0,0);
\coordinate (B) at ($(A)+3*(R)$);
\coordinate (C) at ($(A)+3*0.5*(R)+4*(U)$);

Drawing a triangle

command to draw a triangle.

\myTriangle{(A)}
\myTriangle{(B)}
\myTriangle{(C)}

Drawing legs.

Specify the coordinates of the legs by adding and subtracting vectors, and draw a line.

\draw ($(A)+0.5*(R)+1*(U)$) -- ($(C)$);
\draw ($(B)+0.5*(R)+1*(U)$) -- ($(C)+(R)$);
\draw ($(A)$) -- ($(A)-0.5*(R)-4*(U)$);
\draw ($(A)+(R)$) -- ($(A)+(R)+0.5*(R)-4*(U)$);
\draw ($(B)$) -- ($(B)-0.5*(R)-4*(U)$);
\draw ($(B)+(R)$) -- ($(B)+(R)+0.5*(R)-4*(U)$);

If you define it well, you will be able to do complex drawings.