# 18 19 20 triangle

### Acute scalene triangle.

Sides: a = 18   b = 19   c = 20

Area: T = 155.4499147634
Perimeter: p = 57
Semiperimeter: s = 28.5

Angle ∠ A = α = 54.99003678046° = 54°54'1″ = 0.95881921787 rad
Angle ∠ B = β = 59.72439505476° = 59°43'26″ = 1.04223795794 rad
Angle ∠ C = γ = 65.37656816478° = 65°22'32″ = 1.14110208955 rad

Height: ha = 17.27221275148
Height: hb = 16.3633068172
Height: hc = 15.54549147634

Median: ma = 17.30660682999
Median: mb = 16.48548415218
Median: mc = 15.57224115024

Inradius: r = 5.45443560573
Circumradius: R = 111.0003819643

Vertex coordinates: A[20; 0] B[0; 0] C[9.075; 15.54549147634]
Centroid: CG[9.69216666667; 5.18216382545]
Coordinates of the circumscribed circle: U[10; 4.58334924851]
Coordinates of the inscribed circle: I[9.5; 5.45443560573]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 125.1099632195° = 125°5'59″ = 0.95881921787 rad
∠ B' = β' = 120.2766049452° = 120°16'34″ = 1.04223795794 rad
∠ C' = γ' = 114.6244318352° = 114°37'28″ = 1.14110208955 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.