Angle is represented with the 
icon.
Angle is a simple property that exists only for Pie. More than that, you have to use Angle to display a Pie chart. You can only put a Continuous field on Angle. When you use a field on Angle, the values are used to calculate the angle of the different portions of the Pie.
You now have all the knowledge to build almost every visualization in Tableau. I say almost because some other essential features are waiting for you in Chapter 7, Design Insightful Visualizations - Part 2.
