Reckoning / Shape / Equilateral triangle
Plane figure · Triangles
Equilateral triangle
Three equal sides and three 60° angles.
Dimensions
Results
height h
area A
Formulas
An isosceles triangle with s = b = a: h = √(a² − a²/4).
Checked: the A formula agrees with a Monte Carlo measurement of the shape itself, made from its geometric definition, every time the site is built.
Topology lens
Topologically a disc, like every figure here without a hole: Euler characteristic 1. Stretching turns it into a circle, a square or a star. More on the lens.