# 4 12 13 triangle

### Obtuse scalene triangle.

Sides: a = 4   b = 12   c = 13

Area: T = 23.89442984831
Perimeter: p = 29
Semiperimeter: s = 14.5

Angle ∠ A = α = 17.83986287523° = 17°50'19″ = 0.31113428058 rad
Angle ∠ B = β = 66.78219922566° = 66°46'55″ = 1.16655656459 rad
Angle ∠ C = γ = 95.37993789911° = 95°22'46″ = 1.66546842019 rad

Height: ha = 11.94771492416
Height: hb = 3.98223830805
Height: hc = 3.67660459205

Median: ma = 12.34990890352
Median: mb = 7.51766481892
Median: mc = 6.14441028637

Inradius: r = 1.6487882654
Circumradius: R = 6.5298754134

Vertex coordinates: A[13; 0] B[0; 0] C[1.57769230769; 3.67660459205]
Centroid: CG[4.8598974359; 1.22553486402]
Coordinates of the circumscribed circle: U[6.5; -0.61220707001]
Coordinates of the inscribed circle: I[2.5; 1.6487882654]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 162.1611371248° = 162°9'41″ = 0.31113428058 rad
∠ B' = β' = 113.2188007743° = 113°13'5″ = 1.16655656459 rad
∠ C' = γ' = 84.62106210089° = 84°37'14″ = 1.66546842019 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.