# 13 21 28 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 21   c = 28

Area: T = 129.3833151917
Perimeter: p = 62
Semiperimeter: s = 31

Angle ∠ A = α = 26.10989056776° = 26°6'32″ = 0.45656863682 rad
Angle ∠ B = β = 45.30878989585° = 45°18'28″ = 0.7910772014 rad
Angle ∠ C = γ = 108.5833195364° = 108°35' = 1.89551342714 rad

Height: ha = 19.90551002949
Height: hb = 12.32222049445
Height: hc = 9.24216537084

Median: ma = 23.88799078725
Median: mb = 19.1387659209
Median: mc = 10.44403065089

Inradius: r = 4.17436500618
Circumradius: R = 14.777008383

Vertex coordinates: A[28; 0] B[0; 0] C[9.14328571429; 9.24216537084]
Centroid: CG[12.3810952381; 3.08105512361]
Coordinates of the circumscribed circle: U[14; -4.7076949792]
Coordinates of the inscribed circle: I[10; 4.17436500618]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 153.8911094322° = 153°53'28″ = 0.45656863682 rad
∠ B' = β' = 134.6922101041° = 134°41'32″ = 0.7910772014 rad
∠ C' = γ' = 71.41768046361° = 71°25' = 1.89551342714 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.