To create circles, you can specify various combinations of center, radius, diameter, points on the circumference, and points on other objects.
You can create circles in several ways. The default method is to specify the center and the radius. Three other ways to draw a circle are shown in the illustration.
Draw a Circle Tangent to Other Objects
The tangent point is a point where an object touches another object without intersecting it. To create a circle that is tangent to other objects, select the objects and then specify the radius of the circle. In the illustrations below, the bold circle is the one being drawn, and points 1 and 2 select the objects to which it is tangent.
To create a circle tangent at three points, set running object snaps to Tangent and use the three-point method to create the circle.