If you have made the switch to the Ribbon from the beloved toolbars, there is a new tool that is only available via the ribbon. That’s right, even if you switch back over to “AutoCAD Classic” (toolbars) this circle tool is not available. The tool is Circle with the “Tangent, Tangent, Tangent” option.
The difference between this tool and the “3 Point Circle” may not be very obvious so I decided to show the difference below.
By selecting the Circle, Tangent, Tangent, Tangent tool you select three OBJECTS and a circle is then made to fit Tangentially between these 3 OBJECTS. I am emphasizing “OBJECTS” because that is the main difference between this tool and the 3 Point circle. The 3 Point circle is made to fit within the 3 specific POINTS.
Hopefully the animated picture below make this clear.
AutoCAD Tips 
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thank you! I am just learning cad and help like yours is much appreciated. C Squella