1. The problem statement, all variables and given/known data find the exact value of cos105 deg 2. Relevant equations n/a 3. The attempt at a solution i know up to cos(45+60)= cos45cos60-sin45sin60 i get lost with the converstions to radical numbers, for example sgrt(2/2) or sqrt2. how do i convert into radicals, and how do i convert out of out of them. once i know that, i can finish solving. I was wondering if someone coud guide me through the steps or provide a link doing that. Thanks alot everyone.