# 8 13 18 triangle

### Obtuse scalene triangle.

Sides: a = 8   b = 13   c = 18

Area: T = 46.75993573523
Perimeter: p = 39
Semiperimeter: s = 19.5

Angle ∠ A = α = 23.55664643091° = 23°33'23″ = 0.41111378623 rad
Angle ∠ B = β = 40.49990559185° = 40°29'57″ = 0.70768418697 rad
Angle ∠ C = γ = 115.9444479772° = 115°56'40″ = 2.02436129215 rad

Height: ha = 11.69898393381
Height: hb = 7.1943747285
Height: hc = 5.19554841503

Median: ma = 15.18222264507
Median: mb = 12.31986849948
Median: mc = 5.95881876439

Inradius: r = 2.39879157617
Circumradius: R = 10.00986918747

Vertex coordinates: A[18; 0] B[0; 0] C[6.08333333333; 5.19554841503]
Centroid: CG[8.02877777778; 1.73218280501]
Coordinates of the circumscribed circle: U[9; -4.37988026952]
Coordinates of the inscribed circle: I[6.5; 2.39879157617]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 156.4443535691° = 156°26'37″ = 0.41111378623 rad
∠ B' = β' = 139.5010944081° = 139°30'3″ = 0.70768418697 rad
∠ C' = γ' = 64.05655202276° = 64°3'20″ = 2.02436129215 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.