# 18 19 21 triangle

### Acute scalene triangle.

Sides: a = 18   b = 19   c = 21

Area: T = 159.7549804382
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 53.20218678868° = 53°12'7″ = 0.92985477628 rad
Angle ∠ B = β = 57.69773438194° = 57°41'50″ = 1.00770086193 rad
Angle ∠ C = γ = 69.10107882938° = 69°6'3″ = 1.20660362715 rad

Height: ha = 17.75499782646
Height: hb = 16.81657688823
Height: hc = 15.2144267084

Median: ma = 17.889854382
Median: mb = 17.09553209973
Median: mc = 15.24397506541

Inradius: r = 5.50986139442
Circumradius: R = 11.23994503827

Vertex coordinates: A[21; 0] B[0; 0] C[9.6199047619; 15.2144267084]
Centroid: CG[10.20663492063; 5.07114223613]
Coordinates of the circumscribed circle: U[10.5; 4.0099394581]
Coordinates of the inscribed circle: I[10; 5.50986139442]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 126.7988132113° = 126°47'53″ = 0.92985477628 rad
∠ B' = β' = 122.3032656181° = 122°18'10″ = 1.00770086193 rad
∠ C' = γ' = 110.8999211706° = 110°53'57″ = 1.20660362715 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.