Hello

I'm trying to cut 8 equal grooves that are equally distributed (45 deg apart) into the angled surface of an inverted cone. I have attached the part in question. I have tried using the groove command from toolbox, wrapping, and basically tried to define a plane on the surface of the inverted plane so that I could draw rectangles from which I could then do extruded cuts. I am still a novice and would love to hear some advice on how to proceed.

I made the inverted cone by sketching a trapezoid and doing a revolved boss but I can't seem to draw anything on the angled surface at all!