# 13 13 19 triangle

### Obtuse isosceles triangle.

Sides: a = 13   b = 13   c = 19

Area: T = 84.30441369092
Perimeter: p = 45
Semiperimeter: s = 22.5

Angle ∠ A = α = 43.04990798002° = 43°2'57″ = 0.75113481825 rad
Angle ∠ B = β = 43.04990798002° = 43°2'57″ = 0.75113481825 rad
Angle ∠ C = γ = 93.90218403995° = 93°54'7″ = 1.63988962887 rad

Height: ha = 12.97698672168
Height: hb = 12.97698672168
Height: hc = 8.87441196746

Median: ma = 14.92548115566
Median: mb = 14.92548115566
Median: mc = 8.87441196746

Inradius: r = 3.74768505293
Circumradius: R = 9.52220712699

Vertex coordinates: A[19; 0] B[0; 0] C[9.5; 8.87441196746]
Centroid: CG[9.5; 2.95880398915]
Coordinates of the circumscribed circle: U[9.5; -0.64879515953]
Coordinates of the inscribed circle: I[9.5; 3.74768505293]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 136.95109202° = 136°57'3″ = 0.75113481825 rad
∠ B' = β' = 136.95109202° = 136°57'3″ = 0.75113481825 rad
∠ C' = γ' = 86.09881596005° = 86°5'53″ = 1.63988962887 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    