# 3 12 13 triangle

### Obtuse scalene triangle.

Sides: a = 3   b = 12   c = 13

Area: T = 17.55499287748
Perimeter: p = 28
Semiperimeter: s = 14

Angle ∠ A = α = 13.00328244668° = 13°10″ = 0.2276942099 rad
Angle ∠ B = β = 64.15875871263° = 64°9'27″ = 1.12197611355 rad
Angle ∠ C = γ = 102.8439588407° = 102°50'23″ = 1.79548894191 rad

Height: ha = 11.76999525165
Height: hb = 2.92549881291
Height: hc = 2.76999890423

Median: ma = 12.42197423484
Median: mb = 7.28801098893
Median: mc = 5.85223499554

Inradius: r = 1.25435663411
Circumradius: R = 6.66766937229

Vertex coordinates: A[13; 0] B[0; 0] C[1.30876923077; 2.76999890423]
Centroid: CG[4.76992307692; 0.98999963474]
Coordinates of the circumscribed circle: U[6.5; -1.4811487494]
Coordinates of the inscribed circle: I[2; 1.25435663411]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 166.9977175533° = 166°59'50″ = 0.2276942099 rad
∠ B' = β' = 115.8422412874° = 115°50'33″ = 1.12197611355 rad
∠ C' = γ' = 77.16604115931° = 77°9'37″ = 1.79548894191 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.