## 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