# 18 26 28 triangle

### Acute scalene triangle.

Sides: a = 18   b = 26   c = 28

Area: T = 227.6843991532
Perimeter: p = 72
Semiperimeter: s = 36

Angle ∠ A = α = 38.71992973222° = 38°43'9″ = 0.67657792223 rad
Angle ∠ B = β = 64.62330664748° = 64°37'23″ = 1.12878852827 rad
Angle ∠ C = γ = 76.65876362029° = 76°39'28″ = 1.33879281485 rad

Height: ha = 25.29882212813
Height: hb = 17.51441531948
Height: hc = 16.26331422523

Median: ma = 25.47554784057
Median: mb = 19.62114168703
Median: mc = 17.43655957742

Inradius: r = 6.32545553203
Circumradius: R = 14.38883633538

Vertex coordinates: A[28; 0] B[0; 0] C[7.71442857143; 16.26331422523]
Centroid: CG[11.90547619048; 5.42110474174]
Coordinates of the circumscribed circle: U[14; 3.32203915432]
Coordinates of the inscribed circle: I[10; 6.32545553203]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 141.2810702678° = 141°16'51″ = 0.67657792223 rad
∠ B' = β' = 115.3776933525° = 115°22'37″ = 1.12878852827 rad
∠ C' = γ' = 103.3422363797° = 103°20'32″ = 1.33879281485 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    