# 9 13 20 triangle

### Obtuse scalene triangle.

Sides: a = 9   b = 13   c = 20

Area: T = 44.98998886413
Perimeter: p = 42
Semiperimeter: s = 21

Angle ∠ A = α = 20.20552235834° = 20°12'19″ = 0.35326476776 rad
Angle ∠ B = β = 29.92664348666° = 29°55'35″ = 0.52223148218 rad
Angle ∠ C = γ = 129.868834155° = 129°52'6″ = 2.26766301542 rad

Height: ha = 9.97877530314
Height: hb = 6.90876751756
Height: hc = 4.49899888641

Median: ma = 16.2565768207
Median: mb = 14.08801278403
Median: mc = 5

Inradius: r = 2.13880899353
Circumradius: R = 13.02989855432

Vertex coordinates: A[20; 0] B[0; 0] C[7.8; 4.49899888641]
Centroid: CG[9.26766666667; 1.49766629547]
Coordinates of the circumscribed circle: U[10; -8.35219138098]
Coordinates of the inscribed circle: I[8; 2.13880899353]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 159.7954776417° = 159°47'41″ = 0.35326476776 rad
∠ B' = β' = 150.0743565133° = 150°4'25″ = 0.52223148218 rad
∠ C' = γ' = 50.132165845° = 50°7'54″ = 2.26766301542 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.