# 9 18 20 triangle

### Acute scalene triangle.

Sides: a = 9   b = 18   c = 20

Area: T = 80.9990354364
Perimeter: p = 47
Semiperimeter: s = 23.5

Angle ∠ A = α = 26.7440245925° = 26°44'25″ = 0.46767053342 rad
Angle ∠ B = β = 64.14439833022° = 64°8'38″ = 1.1219523704 rad
Angle ∠ C = γ = 89.11657707729° = 89°6'57″ = 1.55553636154 rad

Height: ha = 17.99878565253
Height: hb = 8.99989282627
Height: hc = 8.09990354364

Median: ma = 18.48664815473
Median: mb = 12.62993309403
Median: mc = 10.12442283657

Inradius: r = 3.4466398058
Circumradius: R = 10.00111909611

Vertex coordinates: A[20; 0] B[0; 0] C[3.925; 8.09990354364]
Centroid: CG[7.975; 2.76996784788]
Coordinates of the circumscribed circle: U[10; 0.15443393667]
Coordinates of the inscribed circle: I[5.5; 3.4466398058]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 153.2659754075° = 153°15'35″ = 0.46767053342 rad
∠ B' = β' = 115.8566016698° = 115°51'22″ = 1.1219523704 rad
∠ C' = γ' = 90.88442292271° = 90°53'3″ = 1.55553636154 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.