# 4 18 20 triangle

### Obtuse scalene triangle.

Sides: a = 4   b = 18   c = 20

Area: T = 32.72661363439
Perimeter: p = 42
Semiperimeter: s = 21

Angle ∠ A = α = 10.47553138432° = 10°28'31″ = 0.18328287167 rad
Angle ∠ B = β = 54.99003678046° = 54°54'1″ = 0.95881921787 rad
Angle ∠ C = γ = 114.6244318352° = 114°37'28″ = 2.00105717581 rad

Height: ha = 16.3633068172
Height: hb = 3.63662373715
Height: hc = 3.27326136344

Median: ma = 18.92108879284
Median: mb = 11.26994276696
Median: mc = 8.36766002653

Inradius: r = 1.55883874449
Circumradius: R = 111.0003819643

Vertex coordinates: A[20; 0] B[0; 0] C[2.3; 3.27326136344]
Centroid: CG[7.43333333333; 1.09108712115]
Coordinates of the circumscribed circle: U[10; -4.58334924851]
Coordinates of the inscribed circle: I[3; 1.55883874449]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 169.5254686157° = 169°31'29″ = 0.18328287167 rad
∠ B' = β' = 125.1099632195° = 125°5'59″ = 0.95881921787 rad
∠ C' = γ' = 65.37656816478° = 65°22'32″ = 2.00105717581 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.