# 11 13 21 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 13   c = 21

Area: T = 60.72222158687
Perimeter: p = 45
Semiperimeter: s = 22.5

Angle ∠ A = α = 26.41438316656° = 26°24'50″ = 0.46110083306 rad
Angle ∠ B = β = 31.7187633276° = 31°43'3″ = 0.55435771316 rad
Angle ∠ C = γ = 121.8698535058° = 121°52'7″ = 2.12770071914 rad

Height: ha = 11.04404028852
Height: hb = 9.34218793644
Height: hc = 5.7833068178

Median: ma = 16.57655844543
Median: mb = 15.45215371404
Median: mc = 5.89549130613

Inradius: r = 2.69987651497
Circumradius: R = 12.36436792442

Vertex coordinates: A[21; 0] B[0; 0] C[9.35771428571; 5.7833068178]
Centroid: CG[10.1199047619; 1.92876893927]
Coordinates of the circumscribed circle: U[10.5; -6.52876768038]
Coordinates of the inscribed circle: I[9.5; 2.69987651497]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 153.5866168334° = 153°35'10″ = 0.46110083306 rad
∠ B' = β' = 148.2822366724° = 148°16'57″ = 0.55435771316 rad
∠ C' = γ' = 58.13114649415° = 58°7'53″ = 2.12770071914 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.