# 12 20 26 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 20   c = 26

Area: T = 115.3733307138
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 26.34329755443° = 26°20'35″ = 0.4659771658 rad
Angle ∠ B = β = 47.69550102928° = 47°41'42″ = 0.83224349664 rad
Angle ∠ C = γ = 105.9622014163° = 105°57'43″ = 1.84993860292 rad

Height: ha = 19.2298884523
Height: hb = 11.53773307138
Height: hc = 8.87548697799

Median: ma = 22.40553565024
Median: mb = 17.60768168617
Median: mc = 10.14988915651

Inradius: r = 3.97883899013
Circumradius: R = 13.52113251548

Vertex coordinates: A[26; 0] B[0; 0] C[8.07769230769; 8.87548697799]
Centroid: CG[11.3598974359; 2.95882899266]
Coordinates of the circumscribed circle: U[13; -3.71883644176]
Coordinates of the inscribed circle: I[9; 3.97883899013]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 153.6577024456° = 153°39'25″ = 0.4659771658 rad
∠ B' = β' = 132.3054989707° = 132°18'18″ = 0.83224349664 rad
∠ C' = γ' = 74.03879858372° = 74°2'17″ = 1.84993860292 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.