# 18 18 28 triangle

### Obtuse isosceles triangle.

Sides: a = 18   b = 18   c = 28

Area: T = 158.3921918986
Perimeter: p = 64
Semiperimeter: s = 32

Angle ∠ A = α = 38.9422441269° = 38°56'33″ = 0.68796738189 rad
Angle ∠ B = β = 38.9422441269° = 38°56'33″ = 0.68796738189 rad
Angle ∠ C = γ = 102.1155117462° = 102°6'54″ = 1.78222450158 rad

Height: ha = 17.59991021095
Height: hb = 17.59991021095
Height: hc = 11.3143708499

Median: ma = 21.74985631709
Median: mb = 21.74985631709
Median: mc = 11.3143708499

Inradius: r = 4.95497474683
Circumradius: R = 14.3198912319

Vertex coordinates: A[28; 0] B[0; 0] C[14; 11.3143708499]
Centroid: CG[14; 3.77112361663]
Coordinates of the circumscribed circle: U[14; -3.005520382]
Coordinates of the inscribed circle: I[14; 4.95497474683]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 141.0587558731° = 141°3'27″ = 0.68796738189 rad
∠ B' = β' = 141.0587558731° = 141°3'27″ = 0.68796738189 rad
∠ C' = γ' = 77.8854882538° = 77°53'6″ = 1.78222450158 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.