Manual/AnimationParameters.html does not list SetTrigger in the part where it lists all SetMethods.

Parameters can be assigned values from a script using functions in the Animator class: SetFloat, SetInt, and SetBool.

Should be changed into: Parameters can be assigned values from a script using functions in the Animator class: SetFloat, SetInt, SetBool and SetTrigger. (with proper link on it, just like on other Set methods)