How to model a diffuser in solidwork?


Check "Circular Sketch Pattern" under "Sketch tool". With this function, this problem should be easy.
Here's a very simple demo using the data you provided.
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Step 1:
Use your data to create the first one and use "Circular Sketch Pattern". Set the numbers of copies to 11.
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Step 2:
Trim to get the sketch below. Then it should be nice and easy