# Category: Triangles

Purple triangle
The purple triangle was a concentration camp badge used by the Nazis to identify Jehovah's Witnesses in Nazi Germany. The purple triangle was introduced in July 1936 with other concentration camps suc
Triangular number
A triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number, other examples being square numbers and cube numbers. The n
Gore (fabrics)
In clothing and similar applications, a gore is a triangular or trapezoidal piece of a textile as might be used in shaping a garment to fit contours of the body. The word is derived from Old English g
Hart circle
The Hart circle is externally tangent to and internally tangent to incircles of the associated triangles ,,, or the other way around. The Hart circle was discovered by Andrew Searle Hart. There are ei
Dragon's Eye (symbol)
According to Rudolf Koch, the Dragon's Eye is an ancient Germanic symbol. The Dragon's Eye is an isosceles or equilateral triangle pointing downward, with a "Y" in the middle connecting the three poin
Eye of Providence
The Eye of Providence (or the All-Seeing Eye of God) is a symbol that depicts an eye, often enclosed in a triangle and surrounded by rays of light or glory, meant to represent divine providence, where
Roberts's triangle theorem
Roberts's triangle theorem, a result in discrete geometry, states that every simple arrangement of lines has at least triangular faces. Thus, three lines form a triangle, four lines form at least two
List of triangle topics
This list of triangle topics includes things related to the geometric shape, either abstractly, as in idealizations studied by geometers, or in triangular arrays such as Pascal's triangle or triangula
Illusory contours
Illusory contours or subjective contours are visual illusions that evoke the perception of an edge without a luminance or color change across that edge. Illusory brightness and depth ordering often ac
Triangle of opposition
In the system of Aristotelian logic, the triangle of opposition is a diagram representing the different ways in which each of the three propositions of the system is logically related ('opposed') to e
Valknut
The valknut is a symbol consisting of three interlocked triangles. It appears on a variety of objects from the archaeological record of the ancient Germanic peoples. The term valknut is a modern devel
Brocard triangle
In geometry, the Brocard triangle of a triangle is a triangle formed by the intersection of lines from a vertex to its corresponding Brocard point and a line from another vertex to its corresponding B
The inverted black triangle (German: schwarzes Dreieck) was an identification badge used in Nazi concentration camps to mark prisoners designated asozial ("asocial") and arbeitsscheu ("work-shy"). The
Penrose triangle
The Penrose triangle, also known as the Penrose tribar, the impossible tribar, or the impossible triangle, is a triangular impossible object, an optical illusion consisting of an object which can be d
Pink triangle
A pink triangle has been a symbol for the LGBTQ+ community, initially intended as a badge of shame, but later reclaimed as a positive symbol of self-identity and love for queerness. In Nazi Germany in
Hess triangle
The Hess triangle is a triangular tile mosaic set in a sidewalk in New York City's West Village neighborhood at the corner of Seventh Avenue and Christopher Street. The plaque reads "Property of the H
Kobon triangle problem
The Kobon triangle problem is an unsolved problem in combinatorial geometry first stated by Kobon Fujimura (1903-1983). The problem asks for the largest number N(k) of nonoverlapping triangles whose s
Similarity system of triangles
A similarity system of triangles is a specific configuration involving a set of triangles. A set of triangles is considered a configuration when all of the triangles share a minimum of one incidence r
Spidron
This article discusses the geometric figure; for the science-fiction character see Spidron (character). In geometry, a spidron is a continuous flat geometric figure composed entirely of triangles, whe
Triangle
A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices A, B, and C is denoted . In Euclidean geometry, any three points, when
5-Con triangles
In geometry, two triangles are said to be 5-Con or almost congruent if they are not congruent triangles but they are similar triangles and share two side lengths (of non-corresponding sides). The 5-Co
Gusset
In sewing, a gusset is a triangular or rhomboidal piece of fabric inserted into a seam to add breadth or reduce stress from tight-fitting clothing. Gussets were used at the shoulders, underarms, and h