# 1 13 13 triangle

### Acute isosceles triangle.

Sides: a = 1   b = 13   c = 13

Area: T = 6.49551905284
Perimeter: p = 27
Semiperimeter: s = 13.5

Angle ∠ A = α = 4.40884550079° = 4°24'30″ = 0.07769420548 rad
Angle ∠ B = β = 87.7965772496° = 87°47'45″ = 1.53223252994 rad
Angle ∠ C = γ = 87.7965772496° = 87°47'45″ = 1.53223252994 rad

Height: ha = 12.99903810568
Height: hb = 0.99992600813
Height: hc = 0.99992600813

Median: ma = 12.99903810568
Median: mb = 6.53883484153
Median: mc = 6.53883484153

Inradius: r = 0.48111252243
Circumradius: R = 6.50548130329

Vertex coordinates: A[13; 0] B[0; 0] C[0.03884615385; 0.99992600813]
Centroid: CG[4.34661538462; 0.33330866938]
Coordinates of the circumscribed circle: U[6.5; 0.25501851166]
Coordinates of the inscribed circle: I[0.5; 0.48111252243]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 175.5921544992° = 175°35'30″ = 0.07769420548 rad
∠ B' = β' = 92.2044227504° = 92°12'15″ = 1.53223252994 rad
∠ C' = γ' = 92.2044227504° = 92°12'15″ = 1.53223252994 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    