# How do you evaluate arccos(1/2) without a calculator?

60^@

#### Spiegazione:

arccos(1/2) means give me the angle that gives a cos(1/2).

If you look at a trig circle in the first quadrant, the angle with a cos(1/2) is 60^@. This is found in the first quadrant because of the restricted domain and range of the function.

Il grafico di f(x) = arccos(x) has domain:[-1,1], & range: [0, pi]
graph{arccos(x) [-5.687, 5.413, -1.287, 4.263]}