triangle

Table of Contents

Introduction References & Edit History Related Topics

Images

Standard lettering of a triangle

Area of a triangle

Pythagorean theorem

Three theorems of congruent triangles

Figure 6: Construction for similar triangles (see text).

Contrasting triangles in Euclidean, elliptic, and hyperbolic spaces.

Fundamental theorem of similarity

Chinese and Greek geometric theorems

triangle inscribed in a circle

Figure 9: If the angles of triangle ABC (representing any triangle) are trisected, then triangle DEF is equilateral.

Discover

King Cobra snake in Malaysia. (reptile)

9 of the World’s Deadliest Snakes

Town of Sisimiut located on the coast of the Davis Strait on Kangerluarsunnguaq Bay, Greenland

The Largest Islands in the World

Entrants falling and tumbling over while chasing the cheese at the 2016 'Cheese Rolling' held at Cooper's Hill, in the Cotswolds, Brockworth England

7 of the World’s Most Dangerous Festivals

Saint Lucia Day. Young girl wears Lucia crown (tinsel halo) with candles. Holds Saint Lucia Day currant laced saffron buns (lussekatter or Lucia's cats). Observed December 13 honor virgin martyr Santa Lucia (St. Lucy). Luciadagen, Christmas, Sweden

7 Winter Solstice Celebrations From Around the World

Srinivasa Ramanujan, Indian mathematician and autodidact.

6 Interesting Facts about Srinivasa Ramanujan

Coriander leaves, fresh green cilantro on wooden background, herbs

Why Does Cilantro Taste Like Soap to Some People?

Facsimile of one of William Henry Ireland's forgeries, a primitive self-portrait of William Shakespeare(tinted engraving). Published for Samuel Ireland, Norfolk Street, Strand, December 1, 1795. (W.H. Ireland, forgery)

The Time a Law Clerk Successfully Forged a New Shakespeare Play to Impress His Dad

triangle: Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Photos

Standard lettering of a triangle

Area of a triangle

Pythagorean theorem

Three theorems of congruent triangles

Figure 6: Construction for similar triangles (see text).

Contrasting triangles in Euclidean, elliptic, and hyperbolic spaces.

Fundamental theorem of similarity

Chinese and Greek geometric theorems

triangle inscribed in a circle

Figure 9: If the angles of triangle ABC (representing any triangle) are trisected, then triangle DEF is equilateral.

See All Images →

Topics

Pascal’s triangle Heron’s formula spherical triangle right triangle trigonometry Bridge of Asses triangle inequality Ceva’s theorem angle Menelaus’ theorem hexagon

Key People

Heron of Alexandria

Greek mathematician