# 10 12 20 triangle

### Obtuse scalene triangle.

Sides: a = 10   b = 12   c = 20

Area: T = 45.59660524607
Perimeter: p = 42
Semiperimeter: s = 21

Angle ∠ A = α = 22.33216450092° = 22°19'54″ = 0.39897607328 rad
Angle ∠ B = β = 27.12767531173° = 27°7'36″ = 0.47334511573 rad
Angle ∠ C = γ = 130.5421601874° = 130°32'30″ = 2.27883807635 rad

Height: ha = 9.11992104921
Height: hb = 7.59993420768
Height: hc = 4.56596052461

Median: ma = 15.71662336455
Median: mb = 14.62987388383
Median: mc = 4.69904157598

Inradius: r = 2.17112405934
Circumradius: R = 13.15990338992

Vertex coordinates: A[20; 0] B[0; 0] C[8.9; 4.56596052461]
Centroid: CG[9.63333333333; 1.52198684154]
Coordinates of the circumscribed circle: U[10; -8.55333720345]
Coordinates of the inscribed circle: I[9; 2.17112405934]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 157.6688354991° = 157°40'6″ = 0.39897607328 rad
∠ B' = β' = 152.8733246883° = 152°52'24″ = 0.47334511573 rad
∠ C' = γ' = 49.45883981265° = 49°27'30″ = 2.27883807635 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.