# 40 66 66 triangle

### Acute isosceles triangle.

Sides: a = 40   b = 66   c = 66

Area: T = 1257.935481548
Perimeter: p = 172
Semiperimeter: s = 86

Angle ∠ A = α = 35.27994027885° = 35°16'46″ = 0.61657417368 rad
Angle ∠ B = β = 72.36602986058° = 72°21'37″ = 1.26329254584 rad
Angle ∠ C = γ = 72.36602986058° = 72°21'37″ = 1.26329254584 rad

Height: ha = 62.89767407741
Height: hb = 38.11992368328
Height: hc = 38.11992368328

Median: ma = 62.89767407741
Median: mb = 43.46326276242
Median: mc = 43.46326276242

Vertex coordinates: A[66; 0] B[0; 0] C[12.12112121212; 38.11992368328]
Centroid: CG[26.04404040404; 12.70664122776]
Coordinates of the circumscribed circle: U[33; 10.49333895124]
Coordinates of the inscribed circle: I[20; 14.62771490172]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 144.7210597212° = 144°43'14″ = 0.61657417368 rad
∠ B' = β' = 107.6439701394° = 107°38'23″ = 1.26329254584 rad
∠ C' = γ' = 107.6439701394° = 107°38'23″ = 1.26329254584 rad

# How did we calculate this triangle? ### 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    