A 2 d triangle........with equal sides......all angles are 60 degrees..................3 60  degree angles.......they sum to 180........but it like full circle.........

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Equilateral triangle

2D shape

In geometry, an equilateral triangle is a triangle in which all three sides are equal. In the familiar Euclidean geometry, an equilateral triangle is also equiangular; that is, all three internal angles are also congruent to each other and are each 60°. Wikipedia

Area: (√3/ 4 ) x (side of equilateral triangle)²

Perimeter: 3 x side of equilateral triangle

Number of vertices: 3

Number of edges: 3

Internal angle: 60°

Type: Regular polygon

Line of symmetry: 3