# 9 21 28 triangle

### Obtuse scalene triangle.

Sides: a = 9   b = 21   c = 28

Area: T = 68.11875454637
Perimeter: p = 58
Semiperimeter: s = 29

Angle ∠ A = α = 13.39767268735° = 13°23'48″ = 0.23438169929 rad
Angle ∠ B = β = 32.72655443586° = 32°43'32″ = 0.57111684986 rad
Angle ∠ C = γ = 133.8787728768° = 133°52'40″ = 2.33766071621 rad

Height: ha = 15.13772323253
Height: hb = 6.48773852823
Height: hc = 4.86655389617

Median: ma = 24.33661870473
Median: mb = 17.9511323071
Median: mc = 8.06222577483

Inradius: r = 2.34988808781
Circumradius: R = 19.42223087604

Vertex coordinates: A[28; 0] B[0; 0] C[7.57114285714; 4.86655389617]
Centroid: CG[11.85771428571; 1.62218463206]
Coordinates of the circumscribed circle: U[14; -13.46220235324]
Coordinates of the inscribed circle: I[8; 2.34988808781]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 166.6033273127° = 166°36'12″ = 0.23438169929 rad
∠ B' = β' = 147.2744455641° = 147°16'28″ = 0.57111684986 rad
∠ C' = γ' = 46.12222712321° = 46°7'20″ = 2.33766071621 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.