How to understand the 'draftangle' of 'Extrude Crv>Tapered tool'

Hi I’m going over Pg 212 of Rhino level 1 training guide. I don’t understand how the draft angle is set to -3 when the distance is .2. How can I calculate the draft angle?

Hi Nathan -

The -3 draft angle is in degrees. The extrusion distance is in inches.

The draft angle is typically a requirement in a production process. That is, it’s an input into the modeling process, not something that you calculate as part of that modeling process.
-wim