# What is the arccos of 0 ?

arccos 0 = ?

The arccosine is the inverse cosine function.

Since

cos 0 = cos 0º = 1

The arccosine of 0 is equal to the inverse cosine function of 0, which is
equal to π/2 radians or 90 degrees:

arccos 0 = cos^{-1} 0 = π/2 rad = 90º

## See also