To Create a Circle Tangent to Three Entities
1. Click Sketch and then click the arrow next to Circle.
2. Click 
3 Tangent.
3 Tangent.3. Select an arc, circle, or line to define the first entity of tangency.
4. Select another arc, circle, or line to define the second tangent entity. The circle is previewed.
5. Select the third tangency point on an arc, circle, or line. The circle is created.