# 10 13 20 triangle

### Obtuse scalene triangle.

Sides: a = 10   b = 13   c = 20

Area: T = 56.14765715783
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 25.58879901207° = 25°35'17″ = 0.44765946766 rad
Angle ∠ B = β = 34.15772224785° = 34°9'26″ = 0.59661559956 rad
Angle ∠ C = γ = 120.2554787401° = 120°15'17″ = 2.09988419814 rad

Height: ha = 11.22993143157
Height: hb = 8.6387934089
Height: hc = 5.61546571578

Median: ma = 16.10990036936
Median: mb = 14.41435353054
Median: mc = 5.87436700622

Inradius: r = 2.61114684455
Circumradius: R = 11.57768422137

Vertex coordinates: A[20; 0] B[0; 0] C[8.275; 5.61546571578]
Centroid: CG[9.425; 1.87215523859]
Coordinates of the circumscribed circle: U[10; -5.8332947423]
Coordinates of the inscribed circle: I[8.5; 2.61114684455]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 154.4122009879° = 154°24'43″ = 0.44765946766 rad
∠ B' = β' = 145.8432777522° = 145°50'34″ = 0.59661559956 rad
∠ C' = γ' = 59.74552125992° = 59°44'43″ = 2.09988419814 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.