How do you evaluate arccos(12)?

1 Answer
Apr 15, 2016

As the range is not specified, the general value is given. The principal value of arccos(12) is 3π4.
The general value is 2kπ±3π4, k = 0. 1. 2. 3.,...

Explanation:

Cosine is positive in the 1st quadrant [0, pi/2] and negative in the second [π2,π]

The principal value for arc cos is defined to be in [0,π].

The general value is 2kπ±(principal value), k = 0. 1. 2. 3.,...

Here, the principal value of arccos(12)=3π4.