# 15 20 28 triangle

### Obtuse scalene triangle.

Sides: a = 15   b = 20   c = 28

Area: T = 144.6377261797
Perimeter: p = 63
Semiperimeter: s = 31.5

Angle ∠ A = α = 31.10218950348° = 31°6'7″ = 0.5432830472 rad
Angle ∠ B = β = 43.53111521674° = 43°31'52″ = 0.76597619325 rad
Angle ∠ C = γ = 105.3676952798° = 105°22'1″ = 1.83990002491 rad

Height: ha = 19.28549682395
Height: hb = 14.46437261797
Height: hc = 10.33112329855

Median: ma = 23.14662739982
Median: mb = 20.11221853611
Median: mc = 10.79435165725

Inradius: r = 4.59216591047
Circumradius: R = 14.51990801728

Vertex coordinates: A[28; 0] B[0; 0] C[10.875; 10.33112329855]
Centroid: CG[12.95883333333; 3.44437443285]
Coordinates of the circumscribed circle: U[14; -3.84875562458]
Coordinates of the inscribed circle: I[11.5; 4.59216591047]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 148.8988104965° = 148°53'53″ = 0.5432830472 rad
∠ B' = β' = 136.4698847833° = 136°28'8″ = 0.76597619325 rad
∠ C' = γ' = 74.63330472022° = 74°37'59″ = 1.83990002491 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.