# 8 16 21 triangle

### Obtuse scalene triangle.

Sides: a = 8   b = 16   c = 21

Area: T = 56.43998005316
Perimeter: p = 45
Semiperimeter: s = 22.5

Angle ∠ A = α = 19.61659069161° = 19°36'57″ = 0.34223621615 rad
Angle ∠ B = β = 42.17772350071° = 42°10'38″ = 0.73661316203 rad
Angle ∠ C = γ = 118.2076858077° = 118°12'25″ = 2.06330988719 rad

Height: ha = 14.10999501329
Height: hb = 7.05499750664
Height: hc = 5.37114095744

Median: ma = 18.23545825288
Median: mb = 13.73295302177
Median: mc = 7.05333679898

Inradius: r = 2.50766578014
Circumradius: R = 11.91549357563

Vertex coordinates: A[21; 0] B[0; 0] C[5.92985714286; 5.37114095744]
Centroid: CG[8.97661904762; 1.79904698581]
Coordinates of the circumscribed circle: U[10.5; -5.63216688535]
Coordinates of the inscribed circle: I[6.5; 2.50766578014]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 160.3844093084° = 160°23'3″ = 0.34223621615 rad
∠ B' = β' = 137.8232764993° = 137°49'22″ = 0.73661316203 rad
∠ C' = γ' = 61.79331419232° = 61°47'35″ = 2.06330988719 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.