# 18 18 18 triangle

### Equilateral triangle.

Sides: a = 18   b = 18   c = 18

Area: T = 140.2966115413
Perimeter: p = 54
Semiperimeter: s = 27

Angle ∠ A = α = 60° = 1.04771975512 rad
Angle ∠ B = β = 60° = 1.04771975512 rad
Angle ∠ C = γ = 60° = 1.04771975512 rad

Height: ha = 15.58884572681
Height: hb = 15.58884572681
Height: hc = 15.58884572681

Median: ma = 15.58884572681
Median: mb = 15.58884572681
Median: mc = 15.58884572681

Inradius: r = 5.19661524227
Circumradius: R = 10.39223048454

Vertex coordinates: A[18; 0] B[0; 0] C[9; 15.58884572681]
Centroid: CG[9; 5.19661524227]
Coordinates of the circumscribed circle: U[9; 5.19661524227]
Coordinates of the inscribed circle: I[9; 5.19661524227]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 120° = 1.04771975512 rad
∠ B' = β' = 120° = 1.04771975512 rad
∠ C' = γ' = 120° = 1.04771975512 rad

# How did we calculate this triangle?

Now we know the lengths of all three sides of the triangle and the triangle is uniquely determined. Next we calculate another its characteristics - same procedure as calculation of the triangle from the known three sides SSS. ### 1. The triangle circumference is the sum of the lengths of its three sides ### 2. Semiperimeter of the triangle ### 3. The triangle area using Heron's formula ### 4. Calculate the heights of the triangle from its area. ### 5. Calculation of the inner angles of the triangle using a Law of Cosines ### 6. Inradius ### 7. Circumradius ### 8. Calculation of medians #### Look also our friend's collection of math examples and problems:

See more informations about triangles or more information about solving triangles.