# 9 20 26 triangle

### Obtuse scalene triangle.

Sides: a = 9   b = 20   c = 26

Area: T = 75.65334037569
Perimeter: p = 55
Semiperimeter: s = 27.5

Angle ∠ A = α = 16.91663146952° = 16°54'59″ = 0.29552453887 rad
Angle ∠ B = β = 40.2876517009° = 40°17'11″ = 0.7033132366 rad
Angle ∠ C = γ = 122.7977168296° = 122°47'50″ = 2.14332148989 rad

Height: ha = 16.81218675015
Height: hb = 7.56553403757
Height: hc = 5.81994925967

Median: ma = 22.7544120506
Median: mb = 16.68883192683
Median: mc = 8.45657672626

Inradius: r = 2.75110328639
Circumradius: R = 15.46552658294

Vertex coordinates: A[26; 0] B[0; 0] C[6.86553846154; 5.81994925967]
Centroid: CG[10.95551282051; 1.94398308656]
Coordinates of the circumscribed circle: U[13; -8.37770189909]
Coordinates of the inscribed circle: I[7.5; 2.75110328639]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 163.0843685305° = 163°5'1″ = 0.29552453887 rad
∠ B' = β' = 139.7133482991° = 139°42'49″ = 0.7033132366 rad
∠ C' = γ' = 57.20328317042° = 57°12'10″ = 2.14332148989 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    