# 4 4 5 triangle

### Acute isosceles triangle.

Sides: a = 4   b = 4   c = 5

Area: T = 7.8066247498
Perimeter: p = 13
Semiperimeter: s = 6.5

Angle ∠ A = α = 51.31878125465° = 51°19'4″ = 0.89656647939 rad
Angle ∠ B = β = 51.31878125465° = 51°19'4″ = 0.89656647939 rad
Angle ∠ C = γ = 77.3644374907° = 77°21'52″ = 1.35502630659 rad

Height: ha = 3.9033123749
Height: hb = 3.9033123749
Height: hc = 3.12224989992

Median: ma = 4.06220192023
Median: mb = 4.06220192023
Median: mc = 3.12224989992

Inradius: r = 1.20109611535
Circumradius: R = 2.56220504609

Vertex coordinates: A[5; 0] B[0; 0] C[2.5; 3.12224989992]
Centroid: CG[2.5; 1.04108329997]
Coordinates of the circumscribed circle: U[2.5; 0.56604485383]
Coordinates of the inscribed circle: I[2.5; 1.20109611535]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 128.6822187453° = 128°40'56″ = 0.89656647939 rad
∠ B' = β' = 128.6822187453° = 128°40'56″ = 0.89656647939 rad
∠ C' = γ' = 102.6365625093° = 102°38'8″ = 1.35502630659 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    