Not invisible to giants or mammoths in Skyrim

I attacked a mammoth, then started running away, then cast muffle, then cast invisibility. Both the mammoth and the giant chased me wherever I went and the mammoth killed me. I had the same result with an invisibility potion instead of the spell.

Why? Can I become undetectable to them?

Solution 1:

What is happening is that you are detected by the Mammoth and Giant when you attack. You have to get far enough away from them first before you can begin to sneak again (since they are so fast this can be hard, I recommend using either a horse or climbing some rocky terrain they cannot get up). Since muffle and invisibility only improve your sneak ability they will not work if you have already been detected.

Sneaking will let you avoid the mammoth and giant or at least get a sneak attack in for bonus damage. If the sneak attack bonus isn't enough I recommend leaving them in peace until you level up.