# 3 18 20 triangle

### Obtuse scalene triangle.

Sides: a = 3   b = 18   c = 20

Area: T = 21.17663429326
Perimeter: p = 41
Semiperimeter: s = 20.5

Angle ∠ A = α = 6.75662861124° = 6°45'23″ = 0.11879194379 rad
Angle ∠ B = β = 44.90105279607° = 44°54'2″ = 0.78436620488 rad
Angle ∠ C = γ = 128.3433185927° = 128°20'35″ = 2.24400111669 rad

Height: ha = 14.11875619551
Height: hb = 2.35329269925
Height: hc = 2.11876342933

Median: ma = 18.96770767384
Median: mb = 11.11330553854
Median: mc = 8.15547532152

Inradius: r = 1.03329923382
Circumradius: R = 12.75500768598

Vertex coordinates: A[20; 0] B[0; 0] C[2.125; 2.11876342933]
Centroid: CG[7.375; 0.70658780978]
Coordinates of the circumscribed circle: U[10; -7.91097699038]
Coordinates of the inscribed circle: I[2.5; 1.03329923382]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 173.2443713888° = 173°14'37″ = 0.11879194379 rad
∠ B' = β' = 135.0999472039° = 135°5'58″ = 0.78436620488 rad
∠ C' = γ' = 51.65768140731° = 51°39'25″ = 2.24400111669 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.