# 11 13 18 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 13   c = 18

Area: T = 70.99329573972
Perimeter: p = 42
Semiperimeter: s = 21

Angle ∠ A = α = 37.35768519729° = 37°21'25″ = 0.65220000651 rad
Angle ∠ B = β = 45.81656148467° = 45°48'56″ = 0.87996333279 rad
Angle ∠ C = γ = 96.82875331804° = 96°49'39″ = 1.69899592606 rad

Height: ha = 12.90878104359
Height: hb = 10.92219934457
Height: hc = 7.88881063775

Median: ma = 14.70554411699
Median: mb = 13.42657215821
Median: mc = 8

Inradius: r = 3.38106170189
Circumradius: R = 9.0644279382

Vertex coordinates: A[18; 0] B[0; 0] C[7.66766666667; 7.88881063775]
Centroid: CG[8.55655555556; 2.62993687925]
Coordinates of the circumscribed circle: U[9; -1.07875716748]
Coordinates of the inscribed circle: I[8; 3.38106170189]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 142.6433148027° = 142°38'35″ = 0.65220000651 rad
∠ B' = β' = 134.1844385153° = 134°11'4″ = 0.87996333279 rad
∠ C' = γ' = 83.17224668196° = 83°10'21″ = 1.69899592606 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.