The four shown circles have the same radius and each one is tangent to one side or two sides of the triangle. Each circle is tangent to the segment which is inside the triangle ABC. Besides, the central lower circle is tangent to its neighbor circles. If AC = 12 cm, what is the value of the area of the triangle ABC?
I tried to assign angle variables to the triangle to compute the sides of the triangle, and so to use Heron's formula to calculate the area, but after all, it appears that some data is missing. I haven't found any book or article which treats these kind of problems.