# 6 20 20 triangle

### Acute isosceles triangle.

Sides: a = 6   b = 20   c = 20

Area: T = 59.32111597999
Perimeter: p = 46
Semiperimeter: s = 23

Angle ∠ A = α = 17.25438531174° = 17°15'14″ = 0.30111365456 rad
Angle ∠ B = β = 81.37330734413° = 81°22'23″ = 1.4220228054 rad
Angle ∠ C = γ = 81.37330734413° = 81°22'23″ = 1.4220228054 rad

Height: ha = 19.77437199333
Height: hb = 5.932211598
Height: hc = 5.932211598

Median: ma = 19.77437199333
Median: mb = 10.86327804912
Median: mc = 10.86327804912

Inradius: r = 2.57991808609
Circumradius: R = 10.11444347485

Vertex coordinates: A[20; 0] B[0; 0] C[0.9; 5.932211598]
Centroid: CG[6.96766666667; 1.97773719933]
Coordinates of the circumscribed circle: U[10; 1.51771652123]
Coordinates of the inscribed circle: I[3; 2.57991808609]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 162.7466146883° = 162°44'46″ = 0.30111365456 rad
∠ B' = β' = 98.62769265587° = 98°37'37″ = 1.4220228054 rad
∠ C' = γ' = 98.62769265587° = 98°37'37″ = 1.4220228054 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    