# 13 18 26 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 18   c = 26

Area: T = 107.6844434808
Perimeter: p = 57
Semiperimeter: s = 28.5

Angle ∠ A = α = 27.39993615864° = 27°23'58″ = 0.47882090726 rad
Angle ∠ B = β = 39.58223055699° = 39°34'56″ = 0.69108415577 rad
Angle ∠ C = γ = 113.0188332844° = 113°1'6″ = 1.97325420232 rad

Height: ha = 16.56768361244
Height: hb = 11.96549372009
Height: hc = 8.28334180622

Median: ma = 21.39550928953
Median: mb = 18.48797186126
Median: mc = 8.80334084308

Inradius: r = 3.77884012213
Circumradius: R = 14.12546040127

Vertex coordinates: A[26; 0] B[0; 0] C[10.01992307692; 8.28334180622]
Centroid: CG[12.00664102564; 2.76111393541]
Coordinates of the circumscribed circle: U[13; -5.52330823383]
Coordinates of the inscribed circle: I[10.5; 3.77884012213]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 152.6010638414° = 152°36'2″ = 0.47882090726 rad
∠ B' = β' = 140.418769443° = 140°25'4″ = 0.69108415577 rad
∠ C' = γ' = 66.98216671563° = 66°58'54″ = 1.97325420232 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.