\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,4/0/B,0.7/2.5/C}

\tkzDefCircle[circum](A,B,C) \tkzGetPoint{O}
\tkzDrawCircle[line width=1.0pt, color=black](O,A)

\tkzDefMidPoint(A,B) \tkzGetPoint{M1}
\tkzDefMidPoint(B,C) \tkzGetPoint{M2}
\tkzDefMidPoint(A,C) \tkzGetPoint{M3}

\tkzFillPolygon[fill=ShapeClr,fill opacity=0.1,inner sep=1cm](A,B,C)


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

\tkzMarkRightAngles[line width=0.5pt, size=.15,color=AngleClr,fill=AngleClr,fill opacity=0.1](O,M1,A O,M2,B O,M3,C)

\tkzDrawSegments[line width=0.5pt,color=black, add=0.4 and 0.4](O,M1 O,M2 O,M3)

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

\tkzMarkSegments[mark=s||,size=2.5](O,A O,B O,C)

\end{tikzpicture}
\end{document}