# 4 11 11 triangle

### Acute isosceles triangle.

Sides: a = 4   b = 11   c = 11

Area: T = 21.63333076528
Perimeter: p = 26
Semiperimeter: s = 13

Angle ∠ A = α = 20.95113633928° = 20°57'5″ = 0.3665670274 rad
Angle ∠ B = β = 79.52443183036° = 79°31'28″ = 1.38879611898 rad
Angle ∠ C = γ = 79.52443183036° = 79°31'28″ = 1.38879611898 rad

Height: ha = 10.81766538264
Height: hb = 3.93333286641
Height: hc = 3.93333286641

Median: ma = 10.81766538264
Median: mb = 6.18546584384
Median: mc = 6.18546584384

Inradius: r = 1.66441005887
Circumradius: R = 5.59332269786

Vertex coordinates: A[11; 0] B[0; 0] C[0.72772727273; 3.93333286641]
Centroid: CG[3.90990909091; 1.31111095547]
Coordinates of the circumscribed circle: U[5.5; 1.01769503597]
Coordinates of the inscribed circle: I[2; 1.66441005887]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 159.0498636607° = 159°2'55″ = 0.3665670274 rad
∠ B' = β' = 100.4765681696° = 100°28'32″ = 1.38879611898 rad
∠ C' = γ' = 100.4765681696° = 100°28'32″ = 1.38879611898 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    