# 12 18 28 triangle

### Obtuse scalene triangle.

Sides: a = 12   b = 18   c = 28

Area: T = 73.64110211771
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 16.9911286937° = 16°59'29″ = 0.29765539012 rad
Angle ∠ B = β = 25.99879769925° = 25°59'53″ = 0.45437502974 rad
Angle ∠ C = γ = 137.0110736071° = 137°39″ = 2.3911288455 rad

Height: ha = 12.27435035295
Height: hb = 8.18223356863
Height: hc = 5.26600729412

Median: ma = 22.76596133535
Median: mb = 19.57703857908
Median: mc = 6.1644414003

Inradius: r = 2.53993455578
Circumradius: R = 20.53220346708

Vertex coordinates: A[28; 0] B[0; 0] C[10.78657142857; 5.26600729412]
Centroid: CG[12.92985714286; 1.75333576471]
Coordinates of the circumscribed circle: U[14; -15.01988031388]
Coordinates of the inscribed circle: I[11; 2.53993455578]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 163.0098713063° = 163°31″ = 0.29765539012 rad
∠ B' = β' = 154.0022023008° = 154°7″ = 0.45437502974 rad
∠ C' = γ' = 42.98992639295° = 42°59'21″ = 2.3911288455 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.