# 12 21 26 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 21   c = 26

Area: T = 123.9299163234
Perimeter: p = 59
Semiperimeter: s = 29.5

Angle ∠ A = α = 26.99875872637° = 26°59'51″ = 0.47111967878 rad
Angle ∠ B = β = 52.66002917273° = 52°36'1″ = 0.91880482782 rad
Angle ∠ C = γ = 100.4022121009° = 100°24'8″ = 1.75223475876 rad

Height: ha = 20.65548605391
Height: hb = 11.80327774509
Height: hc = 9.53330125565

Median: ma = 22.85882589013
Median: mb = 17.31332896932
Median: mc = 11.11330553854

Inradius: r = 4.20109885842
Circumradius: R = 13.2177227949

Vertex coordinates: A[26; 0] B[0; 0] C[7.28884615385; 9.53330125565]
Centroid: CG[11.09661538462; 3.17876708522]
Coordinates of the circumscribed circle: U[13; -2.38664439352]
Coordinates of the inscribed circle: I[8.5; 4.20109885842]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 153.0022412736° = 153°9″ = 0.47111967878 rad
∠ B' = β' = 127.4399708273° = 127°23'59″ = 0.91880482782 rad
∠ C' = γ' = 79.5987878991° = 79°35'52″ = 1.75223475876 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.