The tiles of a tetrad can be made of three arcs with different lengths, but with the same radius.
Two tiles can form a circle with point symmetric dissection lines. The shape of the tetrad is mirror symmetric.
Here is shown, how main vertices can be constructed. The green path from the origin O to the point B can be created individually (See samples below). Next you have to reflect the path from O to D at the origin O.
Other variants of the tetrad with mirror symmetric symmetric outline.
It also is possible to avoid reflected tiles. But then the shape of the tetrad is no longer mirror symmetric.
Here all circle arcs have the same radius.