Triangle (English)
Search for " Triangle " in NRICH | PLUS | maths.org | Google
Definition (keystage 1)
A flat shape with three straight sides.
Definition (keystage 2)
A three-sided polygon.
The sum of the interior angles of a triangle is always 180°.
Triangles can be classified: either by their angles, as acute, obtuse, right-angled or equiangular; or by their sides, as scalene, isosceles or equilateral.
The sum of the interior angles of a triangle is always 180°.
Triangles can be classified: either by their angles, as acute, obtuse, right-angled or equiangular; or by their sides, as scalene, isosceles or equilateral.
Relations
- broader:
- (en) Polygon
- (en) Simplex
- narrower:
- (en) Acute triangle
- (en) Altitude of triangle
- (en) Area of a triangle
- (en) Ceva's Theorem
- (en) Circummedial triangle
- (en) Contact triangle
- (en) Cyclic triangles
- (en) Equilateral triangle
- (en) Isosceles triangle
- (en) Marion's theorem
- (en) Medial triangle
- (en) Obtuse triangle
- (en) Orthic triangle
- (en) Pedal triangle
- (en) Point in a triangle
- (en) Right-angled triangle
- (en) Scalene triangle
- (en) Tangential triangle
- (en) Triangular
- references:
- (en) Three
- referenced:
- (en) Ambiguous case
- (en) Congruent triangles
- (en) Cosine law
- (en) Escribed circle
- (en) Heron's formula
- (en) Hypotenuse
- (en) Menelaus' theorem
- (en) Morley's theorem
- (en) Net of a tetrahedron
- (en) Net of an octahedron
- (en) Octahedron
- (en) Outscribed circle
- (en) Parallel median of a triangle
- (en) Pythagoras' theorem
- (en) Scalene
- (en) Spherical triangle
- (en) Square-based pyramid
- (en) Tetrahedron
- (en) Triangle inequality
- (en) Vertical angle
Funded by: EU Socrates Minerva, HeyMath!, Cambridge University Press