# 12 26 30 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 26   c = 30

Area: T = 154.7132636847
Perimeter: p = 68
Semiperimeter: s = 34

Angle ∠ A = α = 23.37219828432° = 23°22'19″ = 0.40879180533 rad
Angle ∠ B = β = 59.26221313279° = 59°15'44″ = 1.03443193134 rad
Angle ∠ C = γ = 97.3665885829° = 97°21'57″ = 1.69993552868 rad

Height: ha = 25.78554394744
Height: hb = 11.90109720651
Height: hc = 10.31441757898

Median: ma = 27.42326184016
Median: mb = 18.78882942281
Median: mc = 13.60114705087

Inradius: r = 4.5550371672
Circumradius: R = 15.12548149324

Vertex coordinates: A[30; 0] B[0; 0] C[6.13333333333; 10.31441757898]
Centroid: CG[12.04444444444; 3.43880585966]
Coordinates of the circumscribed circle: U[15; -1.93990788375]
Coordinates of the inscribed circle: I[8; 4.5550371672]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 156.6288017157° = 156°37'41″ = 0.40879180533 rad
∠ B' = β' = 120.7387868672° = 120°44'16″ = 1.03443193134 rad
∠ C' = γ' = 82.6344114171° = 82°38'3″ = 1.69993552868 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    