# 11 15 21 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 15   c = 21

Area: T = 79.00875154653
Perimeter: p = 47
Semiperimeter: s = 23.5

Angle ∠ A = α = 30.10882310581° = 30°6'30″ = 0.52554877639 rad
Angle ∠ B = β = 43.1610764259° = 43°9'39″ = 0.7533297444 rad
Angle ∠ C = γ = 106.7311004683° = 106°43'52″ = 1.86328074457 rad

Height: ha = 14.36550028119
Height: hb = 10.53443353954
Height: hc = 7.52545252824

Median: ma = 17.43997126413
Median: mb = 14.99216643506
Median: mc = 7.92114897589

Inradius: r = 3.36220219347
Circumradius: R = 10.9644146827

Vertex coordinates: A[21; 0] B[0; 0] C[8.02438095238; 7.52545252824]
Centroid: CG[9.67546031746; 2.50881750941]
Coordinates of the circumscribed circle: U[10.5; -3.15663452987]
Coordinates of the inscribed circle: I[8.5; 3.36220219347]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 149.8921768942° = 149°53'30″ = 0.52554877639 rad
∠ B' = β' = 136.8399235741° = 136°50'21″ = 0.7533297444 rad
∠ C' = γ' = 73.2698995317° = 73°16'8″ = 1.86328074457 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.