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Similarity Point

External (or positive) and internal (or negative) similarity points of two Circles with centers $C$ and $C'$ and Radii $r$ and $r'$ are the points $E$ and $I$ on the lines $CC'$ such that

\begin{displaymath}
{\it CE\over \it C'E}={r\over r'},
\end{displaymath}

or

\begin{displaymath}
{\it CI\over \it C'I}=-{r\over r'}.
\end{displaymath}




© 1996-9 Eric W. Weisstein
1999-05-26