# 15 19 21 triangle

### Acute scalene triangle.

Sides: a = 15   b = 19   c = 21

Area: T = 137.8122145691
Perimeter: p = 55
Semiperimeter: s = 27.5

Angle ∠ A = α = 43.69224943517° = 43°41'33″ = 0.76325778848 rad
Angle ∠ B = β = 61.04547093922° = 61°2'41″ = 1.06554311698 rad
Angle ∠ C = γ = 75.2632796256° = 75°15'46″ = 1.31435835989 rad

Height: ha = 18.37549527588
Height: hb = 14.50765416517
Height: hc = 13.12549662563

Median: ma = 18.56774446276
Median: mb = 15.58804364509
Median: mc = 13.51985058346

Inradius: r = 5.01113507524
Circumradius: R = 10.85771707704

Vertex coordinates: A[21; 0] B[0; 0] C[7.26219047619; 13.12549662563]
Centroid: CG[9.42106349206; 4.37549887521]
Coordinates of the circumscribed circle: U[10.5; 2.76219118626]
Coordinates of the inscribed circle: I[8.5; 5.01113507524]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 136.3087505648° = 136°18'27″ = 0.76325778848 rad
∠ B' = β' = 118.9555290608° = 118°57'19″ = 1.06554311698 rad
∠ C' = γ' = 104.7377203744° = 104°44'14″ = 1.31435835989 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.