# 10 21 25 triangle

### Obtuse scalene triangle.

Sides: a = 10   b = 21   c = 25

Area: T = 102.8798569197
Perimeter: p = 56
Semiperimeter: s = 28

Angle ∠ A = α = 23.07439180656° = 23°4'26″ = 0.40327158416 rad
Angle ∠ B = β = 55.38991229016° = 55°23'21″ = 0.96767225644 rad
Angle ∠ C = γ = 101.5376959033° = 101°32'13″ = 1.77221542476 rad

Height: ha = 20.57657138394
Height: hb = 9.79879589711
Height: hc = 8.23302855358

Median: ma = 22.53988553392
Median: mb = 15.88223801743
Median: mc = 10.68987791632

Inradius: r = 3.67442346142
Circumradius: R = 12.7587759077

Vertex coordinates: A[25; 0] B[0; 0] C[5.68; 8.23302855358]
Centroid: CG[10.22766666667; 2.74334285119]
Coordinates of the circumscribed circle: U[12.5; -2.55215518154]
Coordinates of the inscribed circle: I[7; 3.67442346142]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 156.9266081934° = 156°55'34″ = 0.40327158416 rad
∠ B' = β' = 124.6110877098° = 124°36'39″ = 0.96767225644 rad
∠ C' = γ' = 78.46330409672° = 78°27'47″ = 1.77221542476 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    