# 17 28 28 triangle

### Acute isosceles triangle.

Sides: a = 17   b = 28   c = 28

Area: T = 226.7688466723
Perimeter: p = 73
Semiperimeter: s = 36.5

Angle ∠ A = α = 35.3444476517° = 35°20'40″ = 0.61768774876 rad
Angle ∠ B = β = 72.32877617415° = 72°19'40″ = 1.2622357583 rad
Angle ∠ C = γ = 72.32877617415° = 72°19'40″ = 1.2622357583 rad

Height: ha = 26.67986431439
Height: hb = 16.19877476231
Height: hc = 16.19877476231

Median: ma = 26.67986431439
Median: mb = 18.45326420872
Median: mc = 18.45326420872

Inradius: r = 6.21328347047
Circumradius: R = 14.69334009307

Vertex coordinates: A[28; 0] B[0; 0] C[5.16107142857; 16.19877476231]
Centroid: CG[11.05435714286; 5.39992492077]
Coordinates of the circumscribed circle: U[14; 4.46604967111]
Coordinates of the inscribed circle: I[8.5; 6.21328347047]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 144.6565523483° = 144°39'20″ = 0.61768774876 rad
∠ B' = β' = 107.6722238259° = 107°40'20″ = 1.2622357583 rad
∠ C' = γ' = 107.6722238259° = 107°40'20″ = 1.2622357583 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    