# 12 18 20 triangle

### Acute scalene triangle.

Sides: a = 12   b = 18   c = 20

Area: T = 106.6543645039
Perimeter: p = 50
Semiperimeter: s = 25

Angle ∠ A = α = 36.33660575146° = 36°20'10″ = 0.63441838408 rad
Angle ∠ B = β = 62.7220387264° = 62°43'13″ = 1.09546772659 rad
Angle ∠ C = γ = 80.94435552214° = 80°56'37″ = 1.41327315469 rad

Height: ha = 17.77656075064
Height: hb = 11.85504050043
Height: hc = 10.66553645039

Median: ma = 18.05554700853
Median: mb = 13.82202749611
Median: mc = 11.57658369028

Inradius: r = 4.26661458015
Circumradius: R = 10.12662361883

Vertex coordinates: A[20; 0] B[0; 0] C[5.5; 10.66553645039]
Centroid: CG[8.5; 3.55551215013]
Coordinates of the circumscribed circle: U[10; 1.59439445852]
Coordinates of the inscribed circle: I[7; 4.26661458015]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 143.6643942485° = 143°39'50″ = 0.63441838408 rad
∠ B' = β' = 117.2879612736° = 117°16'47″ = 1.09546772659 rad
∠ C' = γ' = 99.05664447786° = 99°3'23″ = 1.41327315469 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.