# 8 11 18 triangle

### Obtuse scalene triangle.

Sides: a = 8   b = 11   c = 18

Area: T = 26.99895813232
Perimeter: p = 37
Semiperimeter: s = 18.5

Angle ∠ A = α = 15.82203528829° = 15°49'13″ = 0.27661172466 rad
Angle ∠ B = β = 22.01553695404° = 22°55″ = 0.38442406845 rad
Angle ∠ C = γ = 142.1644277577° = 142°9'51″ = 2.48112347224 rad

Height: ha = 6.74773953308
Height: hb = 4.90771966042
Height: hc = 2.99988423692

Median: ma = 14.37701078632
Median: mb = 12.79664838921
Median: mc = 3.39111649916

Inradius: r = 1.45988962877
Circumradius: R = 14.67223283795

Vertex coordinates: A[18; 0] B[0; 0] C[7.41766666667; 2.99988423692]
Centroid: CG[8.47222222222; 10.9996141231]
Coordinates of the circumscribed circle: U[9; -11.58878047998]
Coordinates of the inscribed circle: I[7.5; 1.45988962877]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 164.1879647117° = 164°10'47″ = 0.27661172466 rad
∠ B' = β' = 157.985463046° = 157°59'5″ = 0.38442406845 rad
∠ C' = γ' = 37.83657224233° = 37°50'9″ = 2.48112347224 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    