# 6 18 21 triangle

### Obtuse scalene triangle.

Sides: a = 6   b = 18   c = 21

Area: T = 50.05993397879
Perimeter: p = 45
Semiperimeter: s = 22.5

Angle ∠ A = α = 15.35988855808° = 15°21'32″ = 0.26880631228 rad
Angle ∠ B = β = 52.61768015821° = 52°37' = 0.91883364295 rad
Angle ∠ C = γ = 112.0244312837° = 112°1'28″ = 1.95551931013 rad

Height: ha = 16.6866446596
Height: hb = 5.56221488653
Height: hc = 4.76875561703

Median: ma = 19.32661480901
Median: mb = 12.5549900398
Median: mc = 8.35216465442

Inradius: r = 2.22548595461
Circumradius: R = 11.32765576894

Vertex coordinates: A[21; 0] B[0; 0] C[3.64328571429; 4.76875561703]
Centroid: CG[8.21442857143; 1.58991853901]
Coordinates of the circumscribed circle: U[10.5; -4.24774591335]
Coordinates of the inscribed circle: I[4.5; 2.22548595461]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 164.6411114419° = 164°38'28″ = 0.26880631228 rad
∠ B' = β' = 127.3833198418° = 127°23' = 0.91883364295 rad
∠ C' = γ' = 67.9765687163° = 67°58'32″ = 1.95551931013 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.