Sector-shaped. It is good to hang fan-shaped calligraphy and paintings in the study. As the name suggests, the fan surface is a surface of the fan shape. The geometric definition of a fan shape is as follows: the figure enclosed by an arc and two radii passing through both ends of the arc is called a fan shape. It is inevitable to mention the fan surface. To think of a fan, a talented person and a beautiful lady, holding a waving fan, are graceful. Throughout Chinese history, calligraphers and painters throughout the ages liked to paint or write on fans to express their emotions, collect them for others, or give them to friends as souvenir poems. Fans used to store calligraphy and paintings are called Chengfan if they are kept as they are, and fans are commonly called fans if they are framed into album pages for the convenience of collection.