Creating Angular Dimensions Using an Imaginary Line

You can use the Smart Dimension tool to create an angle dimension between a line and an imaginary horizontal or vertical line.

1. In an open sketch, click Smart Dimension (Dimensions/Relations toolbar) or Tools > Dimensions > Smart.
2. In a drawing view, select an edge. For example,
   
   
3. Select a collinear vertex. For example,
   
   
4. When the crosshair appears, select one of its segments. For example,
   
   
5. A preview of the angle dimension between the edge and segment appears. Click to place the dimension. For example,