For two pairs of circles (a,b) and (c,d), each pair belonging to a pencil of circles orthogonal to the other pencil (both pencils being parabolic), the intersection points of the circles belong to one circle.
Look at the document Haruki.html for the other case of orthogonal pencils of circles.
![[alogo]](alogo.png){kind=small}
Haruki's theorem ![[0_0]](Haruki2_files/Haruki2_0_0_0.png)
![[0_1]](Haruki2_files/Haruki2_0_0_1.png)
![[0_2]](Haruki2_files/Haruki2_0_0_2.png)
![[1_0]](Haruki2_files/Haruki2_0_1_0.png)
![[1_1]](Haruki2_files/Haruki2_0_1_1.png)
![[1_2]](Haruki2_files/Haruki2_0_1_2.png)
![[2_0]](Haruki2_files/Haruki2_0_2_0.png)
![[2_1]](Haruki2_files/Haruki2_0_2_1.png)
![[2_2]](Haruki2_files/Haruki2_0_2_2.png)