What is the arccosine of 1 ?
arccos 1 = ?
The arccosine is the inverse cosine function.
Since
cos 0 = cos 0º = 1
The arccosine of 1 is equal to the inverse cosine function of 1, which is equal to 0 radians or 0 degrees:
arccos 1 = cos-1 1 = 0 rad = 0º