# 13 13 20 triangle

### Obtuse isosceles triangle.

Sides: a = 13   b = 13   c = 20

Area: T = 83.06662386292
Perimeter: p = 46
Semiperimeter: s = 23

Angle ∠ A = α = 39.71551372318° = 39°42'55″ = 0.69331599076 rad
Angle ∠ B = β = 39.71551372318° = 39°42'55″ = 0.69331599076 rad
Angle ∠ C = γ = 100.5769725536° = 100°34'11″ = 1.75552728384 rad

Height: ha = 12.77994213276
Height: hb = 12.77994213276
Height: hc = 8.30766238629

Median: ma = 15.56443824163
Median: mb = 15.56443824163
Median: mc = 8.30766238629

Inradius: r = 3.61215755926
Circumradius: R = 10.17326045857

Vertex coordinates: A[20; 0] B[0; 0] C[10; 8.30766238629]
Centroid: CG[10; 2.7698874621]
Coordinates of the circumscribed circle: U[10; -1.86659807228]
Coordinates of the inscribed circle: I[10; 3.61215755926]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 140.2854862768° = 140°17'5″ = 0.69331599076 rad
∠ B' = β' = 140.2854862768° = 140°17'5″ = 0.69331599076 rad
∠ C' = γ' = 79.43302744637° = 79°25'49″ = 1.75552728384 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.