I intend to introduce various Sangaku in my blog.
First one is a Sangaku at Sachimiya shrine in Gunma prefecture. The Sangaku was dedicated to the Sachimiya shrine in 1824.
The three circles contact each other and also they are touching on a line, like left diagram.
The diameter of the red circle is 9cm, and the diameter of the white circle is 36cm.
Find the diameter of yellow circle.
(I'll put the solution next time.)
The reference (Japanese): http://www.ene1.me.gunma-u.ac.jp/wasanken/
(The photo image: http://www.ene1.me.gunma-u.ac.jp/wasanken/sangak-corner/satimiya1.htm )