geometry

Geometry notations

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Geometry

$\inline xOy$	The Euclidean plane
$\inline Ox$	The $\inline x$ -axis of the Euclidean plane
$\inline Oy$	The $\inline y$ -axis of the Euclidean plane
$\inline A,\, B,\, C,\, \ldots$	Points in the Euclidean plane with certain coordinates $\inline A(x_A, y_A)$ , $\inline B(x_B, y_B)$ , $\inline C(x_C, y_C)$ , etc.
$\inline AB$	The line that passes through points $\inline A$ and $\inline B$
$\inline A - B - C}$	This says that the points $\inline A$ , $\inline B$ and $\inline C$ are collinear, i.e. there exists a unique line which passes through all of them.
$\inline [AB]$	The segment with endpoints $\inline A$ and $\inline B$
$\inline \|AB\|$	The length of the segment with endpoints $\inline A$ and $\inline B$
$\inline l_1 \parallel l_2$	This says that the lines $\inline l_1$ and $\inline l_2$ are parallel, i.e. they do not have any points in common.
$\inline l_1 \perp l_2$	This says that the lines $\inline l_1$ and $\inline l_2$ are perpendicular, i.e. they form a right angle at their point of intersection.
$\inline d(A, B)$	The distance between the points $\inline A$ and $\inline B$
$\inline d(A, l)$	The distance between the point $\inline A$ and the line $\inline l$
$\inline \angle O, \angle AOB$	The angle with vertex $\inline O$ and rays $\inline OA$ , $\inline OB$
$\inline \triangle ABC$	The triangle with vertices $\inline A$ , $\inline B$ and $\inline C$
$\inline \triangle ABC \equiv \triangle PQR$	This says that the triangles $\inline \triangle ABC$ and $\inline \triangle PQR$ are congruent, which means that $\|AB\| = \|PQ\| \qquad \|AC\| = \|PR\| \qquad \|BC\| = \|QR\|.$
$\inline \triangle ABC \sim \triangle PQR$	This says that the triangles $\inline \triangle ABC$ and $\inline \triangle PQR$ are similar, which basically means $\frac{\|AB\|}{\|PQ\|} = \frac{\|AC\|}{\|PR\|} = \frac{\|BC\|}{\|QR\|}.$
$\inline [ABCD]$	The quadrilateral with vertices $\inline A$ , $\inline B$ , $\inline C$ and $\inline D$
$\inline \mathcal{A}_{\triangle ABC}$	The area of the triangle $\inline \triangle ABC$
$\inline \mathcal{A}_{[ABCD]}$	The area of the quadrilateral $\inline [ABCD]$
$\inline \mathcal{C}(O, R)$	The circle with center at the point $\inline O$ and radius equal to $\inline R$