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