# 12 20 20 triangle

### Acute isosceles triangle.

Sides: a = 12   b = 20   c = 20

Area: T = 114.473270417
Perimeter: p = 52
Semiperimeter: s = 26

Angle ∠ A = α = 34.91552062474° = 34°54'55″ = 0.6099385308 rad
Angle ∠ B = β = 72.54223968763° = 72°32'33″ = 1.26661036728 rad
Angle ∠ C = γ = 72.54223968763° = 72°32'33″ = 1.26661036728 rad

Height: ha = 19.07987840283
Height: hb = 11.4477270417
Height: hc = 11.4477270417

Median: ma = 19.07987840283
Median: mb = 13.11548770486
Median: mc = 13.11548770486

Inradius: r = 4.40327963142
Circumradius: R = 10.48328483672

Vertex coordinates: A[20; 0] B[0; 0] C[3.6; 11.4477270417]
Centroid: CG[7.86766666667; 3.81657568057]
Coordinates of the circumscribed circle: U[10; 3.14548545102]
Coordinates of the inscribed circle: I[6; 4.40327963142]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 145.0854793753° = 145°5'5″ = 0.6099385308 rad
∠ B' = β' = 107.4587603124° = 107°27'27″ = 1.26661036728 rad
∠ C' = γ' = 107.4587603124° = 107°27'27″ = 1.26661036728 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.