# 13 20 20 triangle

### Acute isosceles triangle.

Sides: a = 13   b = 20   c = 20

Area: T = 122.9432822076
Perimeter: p = 53
Semiperimeter: s = 26.5

Angle ∠ A = α = 37.93111499777° = 37°55'52″ = 0.66220234562 rad
Angle ∠ B = β = 71.03444250112° = 71°2'4″ = 1.24397845987 rad
Angle ∠ C = γ = 71.03444250112° = 71°2'4″ = 1.24397845987 rad

Height: ha = 18.91442803194
Height: hb = 12.29442822076
Height: hc = 12.29442822076

Median: ma = 18.91442803194
Median: mb = 13.58330777072
Median: mc = 13.58330777072

Inradius: r = 4.63993517765
Circumradius: R = 10.57440211429

Vertex coordinates: A[20; 0] B[0; 0] C[4.225; 12.29442822076]
Centroid: CG[8.075; 4.09880940692]
Coordinates of the circumscribed circle: U[10; 3.43765568714]
Coordinates of the inscribed circle: I[6.5; 4.63993517765]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 142.0698850022° = 142°4'8″ = 0.66220234562 rad
∠ B' = β' = 108.9665574989° = 108°57'56″ = 1.24397845987 rad
∠ C' = γ' = 108.9665574989° = 108°57'56″ = 1.24397845987 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 ### 6. Inradius ### 7. Circumradius ### 8. Calculation of medians #### Look also our friend's collection of math examples and problems:

See more informations about triangles or more information about solving triangles.