# 8 18 20 triangle

### Obtuse scalene triangle.

Sides: a = 8   b = 18   c = 20

Area: T = 71.93774728497
Perimeter: p = 46
Semiperimeter: s = 23

Angle ∠ A = α = 23.55664643091° = 23°33'23″ = 0.41111378623 rad
Angle ∠ B = β = 64.05655202276° = 64°3'20″ = 1.1187979732 rad
Angle ∠ C = γ = 92.38880154633° = 92°23'17″ = 1.61224750592 rad

Height: ha = 17.98443682124
Height: hb = 7.99330525389
Height: hc = 7.1943747285

Median: ma = 18.60110752377
Median: mb = 12.28882057274
Median: mc = 9.69553597148

Inradius: r = 3.12877162109
Circumradius: R = 10.00986918747

Vertex coordinates: A[20; 0] B[0; 0] C[3.5; 7.1943747285]
Centroid: CG[7.83333333333; 2.39879157617]
Coordinates of the circumscribed circle: U[10; -0.41770288281]
Coordinates of the inscribed circle: I[5; 3.12877162109]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 156.4443535691° = 156°26'37″ = 0.41111378623 rad
∠ B' = β' = 115.9444479772° = 115°56'40″ = 1.1187979732 rad
∠ C' = γ' = 87.61219845367° = 87°36'43″ = 1.61224750592 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.