# How do you evaluate # arccos(-1/sqrt2)#?

##### 1 Answer

Apr 15, 2016

As the range is not specified, the general value is given. The principal value of

The general value is

#### Explanation:

Cosine is positive in the 1st quadrant [0, pi/2] and negative in the second

The principal value for arc cos is defined to be in

The general value is

Here, the principal value of