Vectors d and e are such that |d| = 3 and |e| = 5 and the angle between them is 30 degrees. Determine |d - e|.

I set it up like this:

And did |d-e| = \sqrt{9+25-2(3)(5)(cos30)} = 8.02

However the answer in the book is 2.83. Can anyone tell me where I'm going wrong or if it's a typo? Thanks!