# 19 19 21 triangle

### Acute isosceles triangle.

Sides: a = 19   b = 19   c = 21

Area: T = 166.2688420032
Perimeter: p = 59
Semiperimeter: s = 29.5

Angle ∠ A = α = 56.45222617318° = 56°27'8″ = 0.98552778374 rad
Angle ∠ B = β = 56.45222617318° = 56°27'8″ = 0.98552778374 rad
Angle ∠ C = γ = 67.09554765365° = 67°5'44″ = 1.17110369788 rad

Height: ha = 17.50219389508
Height: hb = 17.50219389508
Height: hc = 15.83550876221

Median: ma = 17.62881025638
Median: mb = 17.62881025638
Median: mc = 15.83550876221

Inradius: r = 5.63662176282
Circumradius: R = 11.3998737052

Vertex coordinates: A[21; 0] B[0; 0] C[10.5; 15.83550876221]
Centroid: CG[10.5; 5.27883625407]
Coordinates of the circumscribed circle: U[10.5; 4.43663505701]
Coordinates of the inscribed circle: I[10.5; 5.63662176282]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 123.5487738268° = 123°32'52″ = 0.98552778374 rad
∠ B' = β' = 123.5487738268° = 123°32'52″ = 0.98552778374 rad
∠ C' = γ' = 112.9054523464° = 112°54'16″ = 1.17110369788 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.