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An angle is a geometric figure formed by two rays (or line segments) that have a common endpoint, known as the vertex. The measure of an angle is typically expressed in degrees or radians and represents the amount of rotation required to align one ray with the other. Angles can be classified into several types based on their measure: 1. **Acute Angle**: Less than 90 degrees. 2. **Right Angle**: Exactly 90 degrees.

"Elementary geometry stubs" typically refers to short articles or entries on topics related to elementary geometry that are found in online encyclopedias or databases, particularly Wikipedia. These stubs contain basic information about a subject but are incomplete, lacking in-depth detail or comprehensive coverage. In the context of Wikipedia, a stub is a type of article that is too short to provide substantial information on its topic, but it has the potential to be expanded by contributors.

Elementary shapes, often referred to as basic or fundamental shapes, are the simplest geometric figures used in mathematics and design. They serve as the foundation for more complex shapes and structures. Some common examples of elementary shapes include: 1. **Point**: A precise location in a space with no dimensions (length, width, or height). 2. **Line**: A straight path that extends infinitely in both directions and has no thickness. It is defined by two points.

Euclidean plane geometry is a branch of mathematics that studies the properties and relationships of points, lines, angles, surfaces, and shapes in a two-dimensional plane. It is named after the ancient Greek mathematician Euclid, who is often referred to as the "father of geometry" due to his influential work, "Elements," which systematically presented the principles and proofs of geometry.

Orthogonality is a concept used in various fields, primarily in mathematics, statistics, and computer science, which describes the idea of two vectors being perpendicular to each other in a specific space. In the context of Euclidean space, two vectors are said to be orthogonal if their dot product is zero.

In geometry, a point is a fundamental concept that represents a precise location in space. It has no length, width, depth, or any other dimensional attribute—essentially, it is a zero-dimensional object. Points are usually denoted by a capital letter (e.g., A, B, C) and can be represented on a coordinate system by ordered pairs or triplets (for two-dimensional or three-dimensional spaces, respectively). Points serve as the building blocks for more complex geometric shapes and constructions.

The AA postulate, or the Angle-Angle similarity postulate, is a fundamental principle in geometry that states that if two triangles have two angles that are equal, then the triangles are similar. This means that their corresponding sides are in proportion, and their corresponding angles are also equal.

The Angle Bisector Theorem is a fundamental principle in geometry that relates the lengths of the sides of a triangle to the segments created by an angle bisector.

Angular diameter (or angular size) is a measure of how large an object appears to an observer, expressed as an angle. It is typically measured in degrees, arcminutes, or arcseconds. Angular diameter is important in fields such as astronomy, where it helps to describe the apparent size of celestial objects (like stars, planets, and galaxies) from a specific point of view, typically from Earth or another observation point.

In mathematics, an annulus (plural: annuli) is a ring-shaped object that is formed by the region between two concentric circles. It can be described in the following way: 1. **Definition**: An annulus is the set of points in a plane that are situated between two circles, typically denoted by an inner circle with radius \( r_1 \) and an outer circle with radius \( r_2 \), where \( r_2 > r_1 \).

In mathematics, the term **antiparallel** typically refers to vectors or lines that are oriented in opposite directions. Specifically, two vectors are said to be antiparallel if they have the same magnitude but point in opposite directions. For example, if vector \( \mathbf{a} \) points to the right (e.g.

Apollonian circles are a fascinating concept in geometry associated with the problem of Apollonius, which involves finding circles that are tangent to three given circles in a plane. The study of these circles reveals insights into various geometric properties, including tangency, curvature, and configuration. In more detail: 1. **Apollonius' Problem**: The classical problem, attributed to Apollonius of Perga, asks for the construction of a circle that is tangent to three given circles.

The Bankoff circle is a concept in the field of mathematics, specifically in geometry. It is associated with the study of triangles and their properties. More precisely, the Bankoff circle is defined in relation to a triangle and its circumcircle. In a triangle, the Bankoff circle is the circle that passes through the triangle's vertices and is tangent to the sides of the triangle at certain points. This circle is named after the mathematician A. Bankoff, who studied its properties.

A bicentric polygon is a type of polygon that possesses both a circumcircle and an incircle. A circumcircle is a circle that passes through all the vertices of the polygon, while an incircle is a circle that is tangent to each side of the polygon. For a polygon to be classified as bicentric, it must meet specific criteria: 1. **Circumcircle**: All the vertices of the polygon lie on a single circle.

A bicone is a geometric shape that resembles two cones joined at their bases. It resembles a double-cone structure and is commonly found in various contexts, including mathematics, geometry, and design. The shape can be characterized by its symmetrical properties and a specific relationship between its height and the radius of its circular base. In computer graphics and 3D modeling, biconic shapes are often used to represent certain types of objects or to create complex designs.

Birkhoff's axioms refer to a set of axioms introduced by mathematician George David Birkhoff in the context of defining the concept of a "relation" in mathematics, particularly pertaining to the fields of algebra and geometry. However, it is important to clarify that Birkhoff is perhaps best known for his work in lattice theory and the foundations of geometry.

Bisection is a mathematical method used to find roots of a continuous function. It is a type of bracketing method, which means it narrows down the search for a root within a certain interval. The key idea behind the bisection method is to divide an interval in half and, based on the signs of the function at the endpoints, determine which half contains the root.

A central angle is an angle whose vertex is at the center of a circle, and whose sides (rays) extend to the circumference of the circle. The central angle is formed between two radii of the circle that connect the center of the circle to two points on its edge. Central angles are important in various mathematical and geometric contexts, particularly in relation to the properties of circles, such as arc length and sector area.

In geometry, the term "centre" typically refers to a specific point that is equidistant from all points on the boundary of a shape or object. The definition of "centre" can vary depending on the geometric figure in question: 1. **Circle**: The centre of a circle is the point that is equidistant from all points on the circumference. This distance is known as the radius.

A circumscribed sphere, also known as a circumsphere, is a sphere that completely encloses a geometric figure, such as a polyhedron or a set of points, in three-dimensional space. The defining property of a circumscribed sphere is that all the vertices (corners) of the figure are located on the surface of the sphere.