# 12 15 25 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 15   c = 25

Area: T = 63.27771680782
Perimeter: p = 52
Semiperimeter: s = 26

Angle ∠ A = α = 19.72333084717° = 19°43'24″ = 0.34442366722 rad
Angle ∠ B = β = 24.95113010927° = 24°57'5″ = 0.43554823567 rad
Angle ∠ C = γ = 135.3255390436° = 135°19'31″ = 2.36218736246 rad

Height: ha = 10.54661946797
Height: hb = 8.43769557438
Height: hc = 5.06221734463

Median: ma = 19.72330829233
Median: mb = 18.1187670932
Median: mc = 5.31550729064

Inradius: r = 2.43437372338
Circumradius: R = 17.77989245974

Vertex coordinates: A[25; 0] B[0; 0] C[10.88; 5.06221734463]
Centroid: CG[11.96; 1.68773911488]
Coordinates of the circumscribed circle: U[12.5; -12.64327908248]
Coordinates of the inscribed circle: I[11; 2.43437372338]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 160.2776691528° = 160°16'36″ = 0.34442366722 rad
∠ B' = β' = 155.0498698907° = 155°2'55″ = 0.43554823567 rad
∠ C' = γ' = 44.67546095644° = 44°40'29″ = 2.36218736246 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    