# 8 21 28 triangle

### Obtuse scalene triangle.

Sides: a = 8   b = 21   c = 28

Area: T = 46.80774513299
Perimeter: p = 57
Semiperimeter: s = 28.5

Angle ∠ A = α = 9.16109877988° = 9°9'40″ = 0.16598893998 rad
Angle ∠ B = β = 24.7043569498° = 24°42'13″ = 0.43111586247 rad
Angle ∠ C = γ = 146.1355442703° = 146°8'8″ = 2.5510544629 rad

Height: ha = 11.70218628325
Height: hb = 4.45878525076
Height: hc = 3.34333893807

Median: ma = 24.42333494836
Median: mb = 17.71329895839
Median: mc = 7.51766481892

Inradius: r = 1.64223667133
Circumradius: R = 25.12442049415

Vertex coordinates: A[28; 0] B[0; 0] C[7.26878571429; 3.34333893807]
Centroid: CG[11.7565952381; 1.11444631269]
Coordinates of the circumscribed circle: U[14; -20.86220630318]
Coordinates of the inscribed circle: I[7.5; 1.64223667133]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 170.8399012201° = 170°50'20″ = 0.16598893998 rad
∠ B' = β' = 155.2966430502° = 155°17'47″ = 0.43111586247 rad
∠ C' = γ' = 33.86545572968° = 33°51'52″ = 2.5510544629 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 ### 6. Inradius ### 7. Circumradius ### 8. Calculation of medians #### Look also our friend's collection of math examples and problems:

See more informations about triangles or more information about solving triangles.