# 17 21 28 triangle

### Obtuse scalene triangle.

Sides: a = 17   b = 21   c = 28

Area: T = 177.989876369
Perimeter: p = 66
Semiperimeter: s = 33

Angle ∠ A = α = 37.25879160013° = 37°15'29″ = 0.65502733067 rad
Angle ∠ B = β = 48.40546480534° = 48°24'17″ = 0.84548204818 rad
Angle ∠ C = γ = 94.33774359453° = 94°20'15″ = 1.64664988651 rad

Height: ha = 20.94398545518
Height: hb = 16.95113108276
Height: hc = 12.71334831207

Median: ma = 23.24332785983
Median: mb = 20.64658228221
Median: mc = 13

Inradius: r = 5.39435988997
Circumradius: R = 14.04402121358

Vertex coordinates: A[28; 0] B[0; 0] C[11.28657142857; 12.71334831207]
Centroid: CG[13.09552380952; 4.23878277069]
Coordinates of the circumscribed circle: U[14; -1.06218647834]
Coordinates of the inscribed circle: I[12; 5.39435988997]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 142.7422083999° = 142°44'31″ = 0.65502733067 rad
∠ B' = β' = 131.5955351947° = 131°35'43″ = 0.84548204818 rad
∠ C' = γ' = 85.66325640547° = 85°39'45″ = 1.64664988651 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    