\documentclass[tikz]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\usepackage{mathrsfs}
\usetikzlibrary{arrows,calc}
\usepackage{tkz-euclide}
\pagestyle{empty}

\definecolor{AngleClr}{rgb}{0,0.39215686274509803,0}
\definecolor{ShapeClr}{rgb}{0.6,0.2,0}

\begin{document}

\begin{tikzpicture}[scale=.75]
\tkzSetUpLine[line width=1pt,color=black]
\tkzSetUpPoint[fill=black]

\tkzDefPoints{0/0/A,0/3.75/B,3.75/0/C,3.75/3.75/D}


\tkzFillPolygon[fill=ShapeClr,fill opacity=0.1](A,B,C)
\tkzMarkRightAngle[line width=1pt, size=.3,color=AngleClr,fill=AngleClr,fill opacity=0.1](B,A,C)
\tkzFillAngles[fill=AngleClr,size=.4,fill opacity=0.1](A,B,C B,C,A)
\tkzMarkAngles[line width=1pt,size=.4,color=AngleClr](A,B,C B,C,A)

\tkzDrawPolygon[color=ShapeClr](A,B,C)
\tkzDrawPoints[size=3](A,B,C,D)
\tkzLabelPoint[below left](A){$\rm A$}
\tkzLabelPoint[above left](B){$\rm B$}
\tkzLabelPoint[below right](C){$\rm \Gamma$}
\tkzLabelPoint[above right](D){$\rm \Delta$}

\tkzLabelAngle(A,B,C){\small $45^\circ$}
\tkzLabelAngle(B,C,A){\small $45^\circ$}

\tkzLabelSegment[left](A,B){$x$}
\tkzLabelSegment(A,C){$x$}
\tkzLabelSegment[above,sloped](B,C){$x \sqrt{2}$}

\tkzDrawSegments[line width=0.5pt,color=black,dashed,dash pattern=on 1pt off 1.75pt](B,D C,D)

\end{tikzpicture}
\end{document}