# 7 12 18 triangle

### Obtuse scalene triangle.

Sides: a = 7   b = 12   c = 18

Area: T = 26.29551991816
Perimeter: p = 37
Semiperimeter: s = 18.5

Angle ∠ A = α = 14.09216737232° = 14°5'30″ = 0.24659461036 rad
Angle ∠ B = β = 24.67695454829° = 24°40'10″ = 0.43105647936 rad
Angle ∠ C = γ = 141.2398780794° = 141°14'20″ = 2.46550817564 rad

Height: ha = 7.51329140519
Height: hb = 4.38325331969
Height: hc = 2.9221688798

Median: ma = 14.89112726118
Median: mb = 12.26878441464
Median: mc = 3.9377003937

Inradius: r = 1.42113621179
Circumradius: R = 14.37552476408

Vertex coordinates: A[18; 0] B[0; 0] C[6.36111111111; 2.9221688798]
Centroid: CG[8.12203703704; 0.9743896266]
Coordinates of the circumscribed circle: U[9; -11.20992704818]
Coordinates of the inscribed circle: I[6.5; 1.42113621179]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 165.9088326277° = 165°54'30″ = 0.24659461036 rad
∠ B' = β' = 155.3330454517° = 155°19'50″ = 0.43105647936 rad
∠ C' = γ' = 38.76112192061° = 38°45'40″ = 2.46550817564 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.