the forth circle@@
There are three Circles(O1,O2,O3). These Circles meet each other.Three yellow green lines are the common chords of the two circles. Then ,the three yellow green lines cross at the one point.
How do you draw the red circle (it meets the three Circles(O1,O2,O3). These Circles meet each other. Three magenda lines are the common chords of the two circles. Then ,the three magenda lines cross at the one point. This point is the same one where the three yellow green lines cross

How do you draw this red circle ?

@You can also move circles (O1,O2,O3) on CABRI.

Download CABRI‡U data (d84) from here.