Reference: How to draw tangent to two touching circles and marking the points
With reference to above link I am trying to make the below figure. But I am not able to make the parts added in the figure by red color. Furthermore I want to draw two right angle marks at points R and I. Please help me.
My MWE:
\documentclass[12pt,a4paper]{article}
\usepackage{tkz-euclide}
\usetkzobj{all}
\begin{document}
\Huge
\begin{tikzpicture}[scale=.8]
\tkzDefPoint(0,0){Origin}
\tkzDefPoint(12,0){O}
\pgfmathsetmacro{\Radius}{4}
\tkzTangent[from with R = O](Origin,\Radius cm) \tkzGetPoints{R}{I}
\tkzDrawCircle[R](Origin,\Radius cm)
\tkzDrawSegments[thick,black,add = 0 and .4](O,R O,I)
\tkzLabelPoints[left,above](R)
\tkzLabelPoints[left,below](I)
\tkzLabelPoints[right](O)
\tkzLabelPoint[left](Origin){$P$}
\end{tikzpicture}
\end{document}


->,\tkzDrawSegments[->,thick,black,add = 0 and .4](O,R O,I)– Salim Bou Jul 27 '16 at 08:38\tkzDrawSegments[thick,red](Origin,R Origin,I)– Salim Bou Jul 27 '16 at 10:42\tkzMarkRightAngle(O,R,P)and\tkzMarkRightAngle(O,I,P). – N. F. Taussig Nov 06 '18 at 02:44