# 2 12 13 triangle

### Obtuse scalene triangle.

Sides: a = 2   b = 12   c = 13

Area: T = 10.79106209275
Perimeter: p = 27
Semiperimeter: s = 13.5

Angle ∠ A = α = 7.95218754307° = 7°57'7″ = 0.1398786408 rad
Angle ∠ B = β = 56.1043644797° = 56°6'13″ = 0.97991933241 rad
Angle ∠ C = γ = 115.9444479772° = 115°56'40″ = 2.02436129215 rad

Height: ha = 10.79106209275
Height: hb = 1.79884368212
Height: hc = 1.66600955273

Median: ma = 12.47699639133
Median: mb = 7.10663352018
Median: mc = 5.63547138348

Inradius: r = 0.79993052539
Circumradius: R = 7.22884996873

Vertex coordinates: A[13; 0] B[0; 0] C[1.11553846154; 1.66600955273]
Centroid: CG[4.70551282051; 0.55333651758]
Coordinates of the circumscribed circle: U[6.5; -3.16224686132]
Coordinates of the inscribed circle: I[1.5; 0.79993052539]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 172.0488124569° = 172°2'53″ = 0.1398786408 rad
∠ B' = β' = 123.8966355203° = 123°53'47″ = 0.97991933241 rad
∠ C' = γ' = 64.05655202276° = 64°3'20″ = 2.02436129215 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    