  Associated to Birkhoff orthogonality, we study Birkhoff angles in a normed
space and present some of their basic properties. We also discuss how to decide
whether an angle is more acute or more obtuse than another. In addition, given
two vectors $x$ and $y$ in a normed space, we study the formula for Birkhoff
`cosine' of the angle from $x$ to $y$ from which we can, in principal, compute
the angle. Some examples will be presented.
