Triangles

thumb|Triangle, a polygon with three corners (vertices) and three lines (sides) A triangle is a polygon with three corners and three sides, one of the basic shapes in geometry. The corners, also called vertices, are zero-dimensional points while the sides connecting them, also called edges, are one-dimensional line segments. A triangle has three internal angles, each one bounded by a pair of adjacent edges; the sum of angles of a triangle always equals a straight angle (180 degrees or π radians). The triangle is a plane figure and its interior is a planar region. Sometimes an arbitrary edge is

figurate number

symbol of the all-seeing eye (usually shown surrounded by rays of glory and/or in a triangle)

impossible object

badge used in Nazi concentration camps to identify homosexual men and transgender women prisoners, later revived in the 1970s as a symbol of protest against homophobia and adopted as a symbol of LGBTQ pride and queer liberation

Nazi concentration camp badge for "asocials"

thumb|Valknut variations.On the left :wikt:unicursal|unicursal trefoil forms; on the right tricursal linked triangle forms.

social model of human interaction consisting of the three roles of victim, rescuer and persecutor

small pin worn on the lapel of a jacket

barycentric plot on three variables

small plot of land in New York City

badge used in Nazi concentration camps to mark primarily Jehovah's Witnesses and some members of other small pacifist religious groups

theory of industrial accident prevention, proposing that if the number of minor accidents is reduced then there will be a corresponding fall in the number of serious accidents

region of Texas, United States

triangle constructed from another triangle

mathematical problem

right|thumb|upright|Late medieval shirt with gussets in the seams at shoulder, underarm, and hem. From a copy of the [[Tacuinum Sanitatis, 14th century.]]

This article discusses the geometric figure; for the science-fiction character see Spidron (character). alt=|thumb|First spidron created by Dániel Erdély in 1979, consisting of equilateral triangles and the symmetrical obtuse [[isosceles triangles which together form right triangles]] In geometry, a spidron is a continuous flat geometric figure composed entirely of triangles, where, for every pair of joining triangles, each has a leg of the other as one of its legs, and neither has any point inside the interior of the other. A deformed spidron is a three-dimensional figure sharing the other pr

visual illusion that evokes the perception of an edge without a luminance or color change across that edge

badge used in Nazi concentration camps to mark political prisoners

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geometry problem

symbol used by Hamas militant group