# 13 13 15 triangle

### Acute isosceles triangle.

Sides: a = 13   b = 13   c = 15

Area: T = 79.6387852181
Perimeter: p = 41
Semiperimeter: s = 20.5

Angle ∠ A = α = 54.76655820154° = 54°45'56″ = 0.95658397229 rad
Angle ∠ B = β = 54.76655820154° = 54°45'56″ = 0.95658397229 rad
Angle ∠ C = γ = 70.46988359692° = 70°28'8″ = 1.23299132077 rad

Height: ha = 12.25219772586
Height: hb = 12.25219772586
Height: hc = 10.61883802908

Median: ma = 12.44398553046
Median: mb = 12.44398553046
Median: mc = 10.61883802908

Inradius: r = 3.88547732771
Circumradius: R = 7.9587899198

Vertex coordinates: A[15; 0] B[0; 0] C[7.5; 10.61883802908]
Centroid: CG[7.5; 3.53994600969]
Coordinates of the circumscribed circle: U[7.5; 2.66604810928]
Coordinates of the inscribed circle: I[7.5; 3.88547732771]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 125.2344417985° = 125°14'4″ = 0.95658397229 rad
∠ B' = β' = 125.2344417985° = 125°14'4″ = 0.95658397229 rad
∠ C' = γ' = 109.5311164031° = 109°31'52″ = 1.23299132077 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.