\begin{definition}[Definition:Orientation of Coordinate Axes/Cartesian 3-Space/Left-Handed]
A Cartesian $3$-Space is defined as being '''left-handed''' if it has the following property:
Let a '''left hand''' be placed such that:
:the thumb and index finger are at right-angles to each other
:the $3$rd finger is at right-angles to the thumb and index finger, upwards from the palm
:the thumb points along the $x$-axis in the positive direction
:the index finger points along the $x$-axis in the positive direction.
Then the $3$rd finger is pointed along the $z$-axis in the positive direction.
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\end{definition}