# 5 17 21 triangle

### Obtuse scalene triangle.

Sides: a = 5   b = 17   c = 21

Area: T = 28.25222123028
Perimeter: p = 43
Semiperimeter: s = 21.5

Angle ∠ A = α = 9.10768257876° = 9°6'25″ = 0.15989440944 rad
Angle ∠ B = β = 32.55769318375° = 32°33'25″ = 0.56882256549 rad
Angle ∠ C = γ = 138.3366242375° = 138°20'10″ = 2.41444229043 rad

Height: ha = 11.30108849211
Height: hb = 3.32437896827
Height: hc = 2.6910686886

Median: ma = 18.94106969249
Median: mb = 12.67987223331
Median: mc = 6.83773971656

Inradius: r = 1.31440563862
Circumradius: R = 15.79552232278

Vertex coordinates: A[21; 0] B[0; 0] C[4.21442857143; 2.6910686886]
Centroid: CG[8.40547619048; 0.89768956287]
Coordinates of the circumscribed circle: U[10.5; -11.87999608819]
Coordinates of the inscribed circle: I[4.5; 1.31440563862]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 170.8933174212° = 170°53'35″ = 0.15989440944 rad
∠ B' = β' = 147.4433068163° = 147°26'35″ = 0.56882256549 rad
∠ C' = γ' = 41.6643757625° = 41°39'50″ = 2.41444229043 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.