diff --git a/math/arctan-pi4.tex b/math/arctan-pi4.tex
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+++ b/math/arctan-pi4.tex
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+\documentclass{standalone}
+%
+\usepackage{tikz}
+\usetikzlibrary{backgrounds,calc}
+\usepackage{tkz-euclide}
+\usetkzobj{all}
+%
+\usepackage{amsmath}
+%
+\usepackage{xcolor}
+%
+\definecolor{space}{HTML}{0A2543}
+\definecolor{earth}{HTML}{0089FA}
+\definecolor{mars}{HTML}{DC7B4E}
+%
+\title{Trigonometry: ArcTan pi/4}
+\begin{document}
+	\begin{tikzpicture}[background rectangle/.style={fill=white},show background rectangle]
+	%
+	\begin{scope}[scale=8]
+		\tkzDefPoint(0,0){O}
+		\tkzDefPoint(2,0){A}
+		\tkzDefPoint(2,1){B}
+		\tkzDrawSquare[fill=space](O,A)
+		%
+		\tkzDrawPolygon[fill=earth](O,A,B)
+		%
+		\tkzDefPoint(3,0){C}
+		\tkzDefPoint(3,1){D}
+		\tkzDefPointBy[rotation = center O angle {atan(1/2)}](C) \tkzGetPoint{C1}
+		\tkzDefPointBy[rotation = center O angle {atan(1/2)}](D) \tkzGetPoint{D1}
+		%
+		\tkzDrawPolygon[fill=mars](O,C1,D1)
+		%
+		\tkzLabelSegment[black,below=2ex,pos=.5](O,A){\fontsize{17}{18}\selectfont $2$}
+		\tkzLabelSegment[black,right=2ex,pos=.5](A,B){\fontsize{17}{18}\selectfont $1$}
+		\tkzLabelSegment[black,below=2ex,pos=0.8](O,C1){\fontsize{17}{18}\selectfont $3$}
+		\tkzLabelSegment[black,right=2ex,pos=.5](C1,D1){\fontsize{17}{18}\selectfont $1$}
+		%
+		\node at (0.5,1.5) {\textcolor{white}{\fontsize{17}{18}\selectfont $\arctan \frac{1}{2} + \arctan \frac{1}{3} = \frac{\pi}{4}$}};
+	\end{scope}
+	%
+	\end{tikzpicture}
+\end{document}
\ No newline at end of file
diff --git a/math/pdf/arctan-pi4.pdf b/math/pdf/arctan-pi4.pdf
new file mode 100644
index 0000000..098b3b1
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