TY - JOUR
T1 - Projections, Birkhoff Orthogonality and Angles in Normed Spaces
AU - Chen , Zhizhi
AU - Lin , Wei
AU - Luo , Lü-Lin
JO - Communications in Mathematical Research 
VL - 4
SP - 378
EP - 384
PY - 2021
DA - 2021/05
SN - 27
DO - http://doi.org/
UR - https://global-sci.org/intro/article_detail/cmr/19081.html
KW - projection, norm, Birkhoff orthogonality, angle, Minkowski plane, duality.
AB - <p style="text-align: justify;">Let $X$ be a Minkowski plane, i.e., a real two dimensional normed linear space. We use projections to give a definition of the angle $A_q(x, y)$ between
two vectors $x$ and $y$ in $X$, such that $x$ is Birkhoff orthogonal to $y$ if and only if $A_q(x, y) =&nbsp;\frac{π}{2}$. Some other properties of this angle are also discussed.</p>