Calculators›Geometry›Triangles

Geometry

Triangles

Triangle areas, perimeters, sides and notable lines.

Area of a triangle

S = a × h / 2→Geometry

Hypotenuse calculator

c = √(a² + b²)→Geometry

Triangle perimeter

P = a + b + c→Geometry

Triangle area using Heron's formula

S = √(p(p−a)(p−b)(p−c))→Geometry

Side using the law of cosines

c = √(a² + b² − 2ab cos γ)→Geometry

Right triangle area

S = a × b / 2→Geometry

Equilateral triangle area

S = a²√3 / 4→Geometry

Triangle median

mₐ = ½√(2b² + 2c² − a²)→Geometry

Triangle semiperimeter

p = P / 2→Geometry

Triangle third angle

γ = 180° − α − β→Geometry

Triangle exterior angle

γext = α + β→Geometry

Triangle area from two sides and angle

S = ab sin γ / 2→Geometry

Side from the law of sines

a = b sin α / sin β→Geometry

Triangle area from inradius and semiperimeter

S = pr→Geometry

Triangle area from sides and circumradius

S = abc / 4R→Geometry

Isosceles triangle from base and height

S = ah/2; b = √((a/2)²+h²)→Geometry

Isosceles triangle perimeter

P = a + 2b→Geometry

Isosceles triangle vertex angle

γ = 2 asin(a / 2b)→Geometry

Equilateral triangle properties

Equilateral triangle properties: calculated from the entered values→Geometry

All triangle properties from three sides

All triangle properties from three sides: calculated from the entered values→Geometry

Right triangle perimeter

P = a + b + c→Geometry

Right triangle area from hypotenuse and altitude

S = ch / 2→Geometry

Altitude to the hypotenuse

h = ab / c→Geometry

Projection of leg a on hypotenuse

m = a² / c→Geometry

Projection of leg b on hypotenuse

n = b² / c→Geometry

Hypotenuse from leg projections

c = m + n→Geometry

Altitude from leg projections

h = √(mn)→Geometry

Complementary acute angle

α = 90° − β→Geometry

Right triangle angle from sine

α = asin(a/c)→Geometry

Right triangle angle from cosine

α = acos(b/c)→Geometry

Right triangle angle from tangent

α = atan(a/b)→Geometry

Leg from hypotenuse and angle α

a = c sin α→Geometry

Leg from hypotenuse and angle β

b = c sin β→Geometry

Median to the hypotenuse

m = c / 2→Geometry

Right triangle inradius

r = (a + b − c) / 2→Geometry

Right triangle circumradius