# 11 18 28 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 18   c = 28

Area: T = 51.17106703102
Perimeter: p = 57
Semiperimeter: s = 28.5

Angle ∠ A = α = 11.71658523949° = 11°42'57″ = 0.2044480199 rad
Angle ∠ B = β = 19.40770433824° = 19°24'25″ = 0.33987168051 rad
Angle ∠ C = γ = 148.8777104223° = 148°52'38″ = 2.59883956495 rad

Height: ha = 9.30437582382
Height: hb = 5.68656300345
Height: hc = 3.65550478793

Median: ma = 22.88655849827
Median: mb = 19.27443352674
Median: mc = 5.14878150705

Inradius: r = 1.79554621161
Circumradius: R = 27.0865828495

Vertex coordinates: A[28; 0] B[0; 0] C[10.375; 3.65550478793]
Centroid: CG[12.79216666667; 1.21883492931]
Coordinates of the circumscribed circle: U[14; -23.18771107571]
Coordinates of the inscribed circle: I[10.5; 1.79554621161]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 168.2844147605° = 168°17'3″ = 0.2044480199 rad
∠ B' = β' = 160.5932956618° = 160°35'35″ = 0.33987168051 rad
∠ C' = γ' = 31.12328957773° = 31°7'22″ = 2.59883956495 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.