# 12 12 20 triangle

### Obtuse isosceles triangle.

Sides: a = 12   b = 12   c = 20

Area: T = 66.33224958071
Perimeter: p = 44
Semiperimeter: s = 22

Angle ∠ A = α = 33.55773097619° = 33°33'26″ = 0.58656855435 rad
Angle ∠ B = β = 33.55773097619° = 33°33'26″ = 0.58656855435 rad
Angle ∠ C = γ = 112.8855380476° = 112°53'7″ = 1.97702215667 rad

Height: ha = 11.05554159679
Height: hb = 11.05554159679
Height: hc = 6.63332495807

Median: ma = 15.36222914957
Median: mb = 15.36222914957
Median: mc = 6.63332495807

Inradius: r = 3.01551134458
Circumradius: R = 10.85444084048

Vertex coordinates: A[20; 0] B[0; 0] C[10; 6.63332495807]
Centroid: CG[10; 2.21110831936]
Coordinates of the circumscribed circle: U[10; -4.22111588241]
Coordinates of the inscribed circle: I[10; 3.01551134458]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 146.4432690238° = 146°26'34″ = 0.58656855435 rad
∠ B' = β' = 146.4432690238° = 146°26'34″ = 0.58656855435 rad
∠ C' = γ' = 67.11546195238° = 67°6'53″ = 1.97702215667 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.