# 13 19 25 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 19   c = 25

Area: T = 121.1954832811
Perimeter: p = 57
Semiperimeter: s = 28.5

Angle ∠ A = α = 30.6833417109° = 30°41' = 0.53655266543 rad
Angle ∠ B = β = 48.22990936801° = 48°13'45″ = 0.842175648 rad
Angle ∠ C = γ = 101.0877489211° = 101°5'15″ = 1.76443095193 rad

Height: ha = 18.64553588939
Height: hb = 12.75773508222
Height: hc = 9.69655866249

Median: ma = 21.23108737456
Median: mb = 17.51442798881
Median: mc = 10.42883268073

Inradius: r = 4.25224502741
Circumradius: R = 12.73877542771

Vertex coordinates: A[25; 0] B[0; 0] C[8.66; 9.69655866249]
Centroid: CG[11.22; 3.23218622083]
Coordinates of the circumscribed circle: U[12.5; -2.45495681302]
Coordinates of the inscribed circle: I[9.5; 4.25224502741]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 149.3176582891° = 149°19' = 0.53655266543 rad
∠ B' = β' = 131.771090632° = 131°46'15″ = 0.842175648 rad
∠ C' = γ' = 78.9132510789° = 78°54'45″ = 1.76443095193 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    