# 11 21 25 triangle

### Obtuse scalene triangle.

Sides: a = 11   b = 21   c = 25

Area: T = 114.4211097268
Perimeter: p = 57
Semiperimeter: s = 28.5

Angle ∠ A = α = 25.84219327632° = 25°50'31″ = 0.45110268118 rad
Angle ∠ B = β = 56.32105874737° = 56°19'14″ = 0.98329796881 rad
Angle ∠ C = γ = 97.83774797631° = 97°50'15″ = 1.70875861537 rad

Height: ha = 20.80438358669
Height: hb = 10.89772473589
Height: hc = 9.15436877814

Median: ma = 22.42220873248
Median: mb = 16.21095650774
Median: mc = 11.16991539518

Inradius: r = 4.01547753427
Circumradius: R = 12.61878653629

Vertex coordinates: A[25; 0] B[0; 0] C[6.1; 9.15436877814]
Centroid: CG[10.36766666667; 3.05112292605]
Coordinates of the circumscribed circle: U[12.5; -1.7210618004]
Coordinates of the inscribed circle: I[7.5; 4.01547753427]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 154.1588067237° = 154°9'29″ = 0.45110268118 rad
∠ B' = β' = 123.6799412526° = 123°40'46″ = 0.98329796881 rad
∠ C' = γ' = 82.16325202369° = 82°9'45″ = 1.70875861537 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    