Rasing your arms up and making yourself look bigger to the coyote might work. I wouldnt' bet on it, especially if I had a shotgun or a pistol with me. We came upon a small den of 'yotes on a pheasant hunt and the coyotes scattered fast, in every direction, but there were many shots fired at them and we got one for sure, maybe two.
I would not hesitate to fire on a wolf, but I've never seen a wolf in the wild.
In March 2010, I saw two really weird dog-like things. There were two dark brown animals that had a lot of long hair and were much larger than a mature coyote. They were within a mile of a place that has large herd of sheep, and when I first saw these big things I thought they might be sheep dogs, so I didn't shoot. I had a clear view of them in my binos. Killing your neighbors sheep dogs is a bad thing. I never found out if the neighbors had large brown sheep dogs, but maybe I will.