# 13 26 30 triangle

### Obtuse scalene triangle.

Sides: a = 13   b = 26   c = 30

Area: T = 168.4439714735
Perimeter: p = 69
Semiperimeter: s = 34.5

Angle ∠ A = α = 25.58879901207° = 25°35'17″ = 0.44765946766 rad
Angle ∠ B = β = 59.74552125992° = 59°44'43″ = 1.04327506722 rad
Angle ∠ C = γ = 94.66767972801° = 94°40' = 1.65222473049 rad

Height: ha = 25.91438022669
Height: hb = 12.95769011335
Height: hc = 11.22993143157

Median: ma = 27.30884236088
Median: mb = 19.11880542943
Median: mc = 14.05334693226

Inradius: r = 4.8822310572
Circumradius: R = 15.05498948778

Vertex coordinates: A[30; 0] B[0; 0] C[6.55; 11.22993143157]
Centroid: CG[12.18333333333; 3.74331047719]
Coordinates of the circumscribed circle: U[15; -1.22444736957]
Coordinates of the inscribed circle: I[8.5; 4.8822310572]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 154.4122009879° = 154°24'43″ = 0.44765946766 rad
∠ B' = β' = 120.2554787401° = 120°15'17″ = 1.04327506722 rad
∠ C' = γ' = 85.33332027199° = 85°20' = 1.65222473049 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    