Line (mathematics) in the context of "Line segment"

In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or ⁠${\displaystyle \pi }$/2⁠ radians corresponding to a quarter turn. If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. The term is a calque of Latin angulus rectus; here rectus means "upright", referring to the vertical perpendicular to a horizontal base line.

Closely related and important geometrical concepts are perpendicular lines, meaning lines that form right angles at their point of intersection, and orthogonality, which is the property of forming right angles, usually applied to vectors. The presence of a right angle in a triangle is the defining factor for right triangles, making the right angle basic to trigonometry.

In mathematics, Pappus's hexagon theorem (attributed to Pappus of Alexandria) states that

• given one set of collinear points ${\displaystyle A,B,C,}$ and another set of collinear points ${\displaystyle a,b,c,}$ then the intersection points ${\displaystyle X,Y,Z}$ of line pairs ${\displaystyle Ab}$ and ${\displaystyle aB,Ac}$ and ${\displaystyle aC,Bc}$ and ${\displaystyle bC}$ are collinear, lying on the Pappus line. These three points are the points of intersection of the "opposite" sides of the hexagon ${\displaystyle AbCaBc}$.

It holds in a projective plane over any field, but fails for projective planes over any noncommutative division ring. Projective planes in which the "theorem" is valid are called pappian planes.

In mathematics, the slope or gradient of a line is a number that describes the direction of the line on a plane. Often denoted by the letter m, slope is calculated as the ratio of the vertical change to the horizontal change ("rise over run") between two distinct points on the line, giving the same A slope is the ratio of the vertical distance (rise) to the horizontal distance (run) between two points, not a direct distance or a direct angle for any choice of points. To explain, a slope is the ratio of the vertical distance (rise) to the horizontal distance (run) between two points, not a direct distance or a direct angleThe line may be physical – as set by a road surveyor, pictorial as in a diagram of a road or roof, or abstract.An application of the mathematical concept is found in the grade or gradient in geography and civil engineering.

The steepness, incline, or grade of a line is the absolute value of its slope: greater absolute value indicates a steeper line. The line trend is defined as follows:

In planetary geology, a ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking somewhat like many thin spokes coming from the hub of a wheel. The rays may extend for lengths up to several times the diameter of their originating crater, and are often accompanied by small secondary craters formed by larger chunks of ejecta. Ray systems have been identified on the Moon, Earth (Kamil Crater), Mercury, and some moons of the outer planets. Originally it was thought that they existed only on planets or moons lacking an atmosphere, but more recently they have been identified on Mars in infrared images taken from orbit by 2001 Mars Odyssey's thermal imager.

Rays appear at visible, and in some cases infrared wavelengths, when ejecta are made of material with different reflectivity (i.e., albedo) or thermal properties from the surface on which they are deposited. Typically, visible rays have a higher albedo than the surrounding surface. More rarely an impact will excavate low albedo material, for example basaltic-lava deposits on the lunar maria. Thermal rays, as seen on Mars, are especially apparent at night when slopes and shadows do not influence the infrared energy emitted by the Martian surface.

In geometry, a conical surface is an unbounded surface in three-dimensional space formed from the union of infinite lines that pass through a fixed point and a space curve.

In mathematics, especially in geometry and topology, an ambient space is the space surrounding a mathematical object along with the object itself. For example, a 1-dimensional line ${\displaystyle (l)}$ may be studied in isolation —in which case the ambient space of ${\displaystyle l}$ is ${\displaystyle l}$, or it may be studied as an object embedded in 2-dimensional Euclidean space ${\displaystyle (\mathbb {R} ^{2})}$—in which case the ambient space of ${\displaystyle l}$ is ${\displaystyle \mathbb {R} ^{2}}$, or as an object embedded in 2-dimensional hyperbolic space ${\displaystyle (\mathbb {H} ^{2})}$—in which case the ambient space of ${\displaystyle l}$ is ${\displaystyle \mathbb {H} ^{2}}$. To see why this makes a difference, consider the statement "Parallel lines never intersect." This is true if the ambient space is ${\displaystyle \mathbb {R} ^{2}}$, but false if the ambient space is ${\displaystyle \mathbb {H} ^{2}}$, because the geometric properties of ${\displaystyle \mathbb {R} ^{2}}$ are different from the geometric properties of ${\displaystyle \mathbb {H} ^{2}}$. All spaces are subsets of their ambient space.

In geometry, bisection is the division of something into two equal or congruent parts (having the same shape and size). Usually it involves a bisecting line, also called a bisector. The most often considered types of bisectors are the segment bisector, a line that passes through the midpoint of a given segment, and the angle bisector, a line that passes through the apex of an angle (that divides it into two equal angles).In three-dimensional space, bisection is usually done by a bisecting plane, also called the bisector.