\documentclass[tikz]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\usepackage{mathrsfs}
\usetikzlibrary{arrows,calc}
\usepackage{tkz-euclide}
\usepackage{fp}
\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/B,0.8/3.7/A,5/0/C}
\tkzDefTriangleCenter[circum](A,B,C) \tkzGetPoint{O}
\tkzDefPointBy[rotation=center O angle -50](A) \tkzGetPoint{P}
\tkzFillPolygon[fill=ShapeClr,fill opacity=0.1](A,B,C)
\tkzDefPointBy[projection = onto B--C](P) \tkzGetPoint{PA}
\tkzDefPointBy[projection = onto A--C](P) \tkzGetPoint{PB}
\tkzDefPointBy[projection = onto A--B](P) \tkzGetPoint{PC}
\tkzMarkRightAngle[line width=0.5pt, size=.15,color=AngleClr,fill=AngleClr,fill opacity=0.1](P,PA,C)
\tkzMarkRightAngle[line width=0.5pt, size=.15,color=AngleClr,fill=AngleClr,fill opacity=0.1](P,PB,A)
\tkzMarkRightAngle[line width=0.5pt, size=.15,color=AngleClr,fill=AngleClr,fill opacity=0.1](P,PC,B)
\tkzDrawSegments[line width=0.5pt,color=black,dashed,dash pattern=on 1pt off 1.75pt,add=0 and 0.4](B,A)
\tkzDrawPolygon[color=ShapeClr](A,B,C)
\tkzDrawSegments[line width=0.5pt,color=black,dashed,dash pattern=on 1pt off 1.75pt](P,PA P,PB P,PC)
\tkzDrawSegments[line width=0.75pt,color=red,add=0.3 and 0.2](PA,PC)
\tkzDrawCircle[color=black,line width=0.5pt](O,A)
\tkzDrawPoints[size=3](A,B,C,P)
\tkzDrawPoints[size=2](PA,PB,PC)
\tkzLabelPoint[above](A){$\mathrm{A}$}
\tkzLabelPoint[below left](B){$\mathrm{B}$}
\tkzLabelPoint[below right](C){$\mathrm{\Gamma}$}
\tkzLabelPoint[below](PA){$\mathrm{P_A}$}
\tkzLabelPoint[below left](PB){$\mathrm{P_B}$}
\tkzLabelPoint[left](PC){$\mathrm{P_\Gamma}$}
\tkzLabelPoint[above right](P){$\mathrm{P}$}
\end{tikzpicture}
\end{document}