# 18 18 19 triangle

### Acute isosceles triangle.

Sides: a = 18   b = 18   c = 19

Area: T = 145.2444406088
Perimeter: p = 55
Semiperimeter: s = 27.5

Angle ∠ A = α = 58.1454569176° = 58°8'40″ = 1.01548141743 rad
Angle ∠ B = β = 58.1454569176° = 58°8'40″ = 1.01548141743 rad
Angle ∠ C = γ = 63.71108616481° = 63°42'39″ = 1.1121964305 rad

Height: ha = 16.13882673432
Height: hb = 16.13882673432
Height: hc = 15.28988848514

Median: ma = 16.17109616288
Median: mb = 16.17109616288
Median: mc = 15.28988848514

Inradius: r = 5.28216147669
Circumradius: R = 10.59659330307

Vertex coordinates: A[19; 0] B[0; 0] C[9.5; 15.28988848514]
Centroid: CG[9.5; 5.09662949505]
Coordinates of the circumscribed circle: U[9.5; 4.69329518207]
Coordinates of the inscribed circle: I[9.5; 5.28216147669]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 121.8555430824° = 121°51'20″ = 1.01548141743 rad
∠ B' = β' = 121.8555430824° = 121°51'20″ = 1.01548141743 rad
∠ C' = γ' = 116.2899138352° = 116°17'21″ = 1.1121964305 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.