# 11 18 26 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 18   c = 26

Area: T = 80.41110533447
Perimeter: p = 55
Semiperimeter: s = 27.5

Angle ∠ A = α = 20.0998614156° = 20°5'55″ = 0.35107869921 rad
Angle ∠ B = β = 34.21660511313° = 34°12'58″ = 0.59771827493 rad
Angle ∠ C = γ = 125.6855334713° = 125°41'7″ = 2.19436229122 rad

Height: ha = 14.62201915172
Height: hb = 8.93545614827
Height: hc = 6.18554656419

Median: ma = 21.67437168017
Median: mb = 17.81985296812
Median: mc = 7.31443694192

Vertex coordinates: A[26; 0] B[0; 0] C[9.09661538462; 6.18554656419]
Centroid: CG[11.69987179487; 2.06218218806]
Coordinates of the circumscribed circle: U[13; -9.3366403004]
Coordinates of the inscribed circle: I[9.5; 2.92440383034]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 159.9011385844° = 159°54'5″ = 0.35107869921 rad
∠ B' = β' = 145.7843948869° = 145°47'2″ = 0.59771827493 rad
∠ C' = γ' = 54.31546652873° = 54°18'53″ = 2.19436229122 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    