# 12 20 28 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 20   c = 28

Area: T = 103.9233048454
Perimeter: p = 60
Semiperimeter: s = 30

Angle ∠ A = α = 21.78767892983° = 21°47'12″ = 0.38802512067 rad
Angle ∠ B = β = 38.21332107017° = 38°12'48″ = 0.66769463445 rad
Angle ∠ C = γ = 120° = 2.09443951024 rad

Height: ha = 17.32105080757
Height: hb = 10.39223048454
Height: hc = 7.42330748896

Median: ma = 23.58796522451
Median: mb = 19.07987840283
Median: mc = 8.71877978871

Inradius: r = 3.46441016151
Circumradius: R = 16.16658075373

Vertex coordinates: A[28; 0] B[0; 0] C[9.42985714286; 7.42330748896]
Centroid: CG[12.47661904762; 2.47443582965]
Coordinates of the circumscribed circle: U[14; -8.08329037687]
Coordinates of the inscribed circle: I[10; 3.46441016151]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 158.2133210702° = 158°12'48″ = 0.38802512067 rad
∠ B' = β' = 141.7876789298° = 141°47'12″ = 0.66769463445 rad
∠ C' = γ' = 60° = 2.09443951024 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.