# 18 19 28 triangle

### Obtuse scalene triangle.

Sides: a = 18   b = 19   c = 28

Area: T = 169.1999401595
Perimeter: p = 65
Semiperimeter: s = 32.5

Angle ∠ A = α = 39.50107243938° = 39°30'3″ = 0.68994176976 rad
Angle ∠ B = β = 42.17772350071° = 42°10'38″ = 0.73661316203 rad
Angle ∠ C = γ = 98.32220405992° = 98°19'19″ = 1.71660433357 rad

Height: ha = 18.87999335105
Height: hb = 17.81104633258
Height: hc = 12.08656715425

Median: ma = 22.17697992774
Median: mb = 21.53548554674
Median: mc = 12.10437184369

Inradius: r = 5.20661354337
Circumradius: R = 14.14989862106

Vertex coordinates: A[28; 0] B[0; 0] C[13.33992857143; 12.08656715425]
Centroid: CG[13.78797619048; 4.02985571808]
Coordinates of the circumscribed circle: U[14; -2.04878795831]
Coordinates of the inscribed circle: I[13.5; 5.20661354337]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 140.4999275606° = 140°29'57″ = 0.68994176976 rad
∠ B' = β' = 137.8232764993° = 137°49'22″ = 0.73661316203 rad
∠ C' = γ' = 81.67879594008° = 81°40'41″ = 1.71660433357 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    