[Tex/LaTex] Tikz, tangent between two circles


I am trying to create the image below

enter image description here

Here is my code


\tkzDrawCircle[very thick,color=blue,fill=green!80!black,opacity=0.6](O,A2)


My problem is, how Do I create the tangent line? And is there a more efficent way than mine? =)

Best Answer

If the tangent is horizontal, then no trig is needed and the following works.

\draw[thick,fill=green!20] (0,0) circle (2cm);
\path[clip] (0,0) circle (2cm);
\fill[green!30] (0,0) circle (2cm);
\draw[thick,blue,fill=white] (0,0) circle (1cm);
\draw[thick,red] (-2,1) -- (2,1) node[midway,above,black] {A};

Note that this is pretty minimal, and just for generating the image you want. More sophisticated methods are available (see Jake's answer), but often I'll default to quick-and-dirty like this, because as much as I love making diagrams, time is money!

enter image description here