# 11 21 28 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 21   c = 28

Area: T = 101.2921658097
Perimeter: p = 60
Semiperimeter: s = 30

Angle ∠ A = α = 20.15330742571° = 20°9'11″ = 0.35217375002 rad
Angle ∠ B = β = 41.1287590142° = 41°7'39″ = 0.71878118614 rad
Angle ∠ C = γ = 118.7199335601° = 118°43'10″ = 2.0722043292 rad

Height: ha = 18.41766651085
Height: hb = 9.64768245806
Height: hc = 7.23551184355

Median: ma = 24.1329857024
Median: mb = 18.5
Median: mc = 9.22195444573

Inradius: r = 3.37663886032
Circumradius: R = 15.96438022556

Vertex coordinates: A[28; 0] B[0; 0] C[8.28657142857; 7.23551184355]
Centroid: CG[12.09552380952; 2.41217061452]
Coordinates of the circumscribed circle: U[14; -7.6710917967]
Coordinates of the inscribed circle: I[9; 3.37663886032]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 159.8476925743° = 159°50'49″ = 0.35217375002 rad
∠ B' = β' = 138.8722409858° = 138°52'21″ = 0.71878118614 rad
∠ C' = γ' = 61.28106643991° = 61°16'50″ = 2.0722043292 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.