# 17 18 28 triangle

### Obtuse scalene triangle.

Sides: a = 17   b = 18   c = 28

Area: T = 146.9066220086
Perimeter: p = 63
Semiperimeter: s = 31.5

Angle ∠ A = α = 35.65990876961° = 35°39'33″ = 0.62223684886 rad
Angle ∠ B = β = 38.11658121692° = 38°6'57″ = 0.66552464194 rad
Angle ∠ C = γ = 106.2255100135° = 106°13'30″ = 1.85439777456 rad

Height: ha = 17.2833084716
Height: hb = 16.32329133429
Height: hc = 10.49333014347

Median: ma = 21.94988040676
Median: mb = 21.34224459704
Median: mc = 10.51218980208

Inradius: r = 4.66436895265
Circumradius: R = 14.58107304738

Vertex coordinates: A[28; 0] B[0; 0] C[13.375; 10.49333014347]
Centroid: CG[13.79216666667; 3.49877671449]
Coordinates of the circumscribed circle: U[14; -4.07440276324]
Coordinates of the inscribed circle: I[13.5; 4.66436895265]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 144.3410912304° = 144°20'27″ = 0.62223684886 rad
∠ B' = β' = 141.8844187831° = 141°53'3″ = 0.66552464194 rad
∠ C' = γ' = 73.77548998653° = 73°46'30″ = 1.85439777456 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    