# 10 12 18 triangle

### Obtuse scalene triangle.

Sides: a = 10   b = 12   c = 18

Area: T = 56.56985424949
Perimeter: p = 40
Semiperimeter: s = 20

Angle ∠ A = α = 31.58663380965° = 31°35'11″ = 0.55112855984 rad
Angle ∠ B = β = 38.9422441269° = 38°56'33″ = 0.68796738189 rad
Angle ∠ C = γ = 109.4711220634° = 109°28'16″ = 1.91106332362 rad

Height: ha = 11.3143708499
Height: hb = 9.42880904158
Height: hc = 6.28553936105

Median: ma = 14.45768322948
Median: mb = 13.26664991614
Median: mc = 6.40331242374

Inradius: r = 2.82884271247
Circumradius: R = 9.5465941546

Vertex coordinates: A[18; 0] B[0; 0] C[7.77877777778; 6.28553936105]
Centroid: CG[8.59325925926; 2.09551312035]
Coordinates of the circumscribed circle: U[9; -3.18219805153]
Coordinates of the inscribed circle: I[8; 2.82884271247]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 148.4143661903° = 148°24'49″ = 0.55112855984 rad
∠ B' = β' = 141.0587558731° = 141°3'27″ = 0.68796738189 rad
∠ C' = γ' = 70.52987793655° = 70°31'44″ = 1.91106332362 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.