# 13 15 15 triangle

### Acute isosceles triangle.

Sides: a = 13   b = 15   c = 15

Area: T = 87.87702879249
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 51.35985772389° = 51°21'31″ = 0.8966376272 rad
Angle ∠ B = β = 64.32107113805° = 64°19'15″ = 1.12326081908 rad
Angle ∠ C = γ = 64.32107113805° = 64°19'15″ = 1.12326081908 rad

Height: ha = 13.51985058346
Height: hb = 11.716603839
Height: hc = 11.716603839

Median: ma = 13.51985058346
Median: mb = 11.86438105177
Median: mc = 11.86438105177

Inradius: r = 4.0876990136
Circumradius: R = 8.32219256164

Vertex coordinates: A[15; 0] B[0; 0] C[5.63333333333; 11.716603839]
Centroid: CG[6.87877777778; 3.905534613]
Coordinates of the circumscribed circle: U[7.5; 3.60661677671]
Coordinates of the inscribed circle: I[6.5; 4.0876990136]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 128.6411422761° = 128°38'29″ = 0.8966376272 rad
∠ B' = β' = 115.6799288619° = 115°40'45″ = 1.12326081908 rad
∠ C' = γ' = 115.6799288619° = 115°40'45″ = 1.12326081908 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.