# 7 18 20 triangle

### Obtuse scalene triangle.

Sides: a = 7   b = 18   c = 20

Area: T = 62.63773490818
Perimeter: p = 45
Semiperimeter: s = 22.5

Angle ∠ A = α = 20.36441348063° = 20°21'51″ = 0.35554212017 rad
Angle ∠ B = β = 63.48552253657° = 63°29'7″ = 1.1088026209 rad
Angle ∠ C = γ = 96.15106398279° = 96°9'2″ = 1.67881452429 rad

Height: ha = 17.8966385452
Height: hb = 6.96597054535
Height: hc = 6.26437349082

Median: ma = 18.70216042093
Median: mb = 11.97991485507
Median: mc = 9.30105376189

Inradius: r = 2.78438821814
Circumradius: R = 10.05878969135

Vertex coordinates: A[20; 0] B[0; 0] C[3.125; 6.26437349082]
Centroid: CG[7.70883333333; 2.08879116361]
Coordinates of the circumscribed circle: U[10; -1.07876318122]
Coordinates of the inscribed circle: I[4.5; 2.78438821814]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 159.6365865194° = 159°38'9″ = 0.35554212017 rad
∠ B' = β' = 116.5154774634° = 116°30'53″ = 1.1088026209 rad
∠ C' = γ' = 83.84993601721° = 83°50'58″ = 1.67881452429 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.