# 8 20 25 triangle

### Obtuse scalene triangle.

Sides: a = 8   b = 20   c = 25

Area: T = 69.13770920708
Perimeter: p = 53
Semiperimeter: s = 26.5

Angle ∠ A = α = 16.05443080743° = 16°3'16″ = 0.2880200535 rad
Angle ∠ B = β = 43.73987273265° = 43°44'19″ = 0.76333848025 rad
Angle ∠ C = γ = 120.2076964599° = 120°12'25″ = 2.09880073161 rad

Height: ha = 17.28442730177
Height: hb = 6.91437092071
Height: hc = 5.53109673657

Median: ma = 22.28222799552
Median: mb = 15.63664957711
Median: mc = 8.70334475928

Inradius: r = 2.60989468706
Circumradius: R = 14.46440159146

Vertex coordinates: A[25; 0] B[0; 0] C[5.78; 5.53109673657]
Centroid: CG[10.26; 1.84436557886]
Coordinates of the circumscribed circle: U[12.5; -7.2777208007]
Coordinates of the inscribed circle: I[6.5; 2.60989468706]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 163.9465691926° = 163°56'44″ = 0.2880200535 rad
∠ B' = β' = 136.2611272674° = 136°15'41″ = 0.76333848025 rad
∠ C' = γ' = 59.79330354007° = 59°47'35″ = 2.09880073161 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    