# 15 21 28 triangle

### Obtuse scalene triangle.

Sides: a = 15   b = 21   c = 28

Area: T = 154.7132636847
Perimeter: p = 64
Semiperimeter: s = 32

Angle ∠ A = α = 31.75113162564° = 31°45'5″ = 0.55441650105 rad
Angle ∠ B = β = 47.4533334116° = 47°27'12″ = 0.82882169214 rad
Angle ∠ C = γ = 100.7955349628° = 100°47'43″ = 1.75992107217 rad

Height: ha = 20.62883515795
Height: hb = 14.73545368425
Height: hc = 11.05109026319

Median: ma = 23.58549528301
Median: mb = 19.85657296517
Median: mc = 11.70546999107

Inradius: r = 4.83547699015
Circumradius: R = 14.25222294555

Vertex coordinates: A[28; 0] B[0; 0] C[10.14328571429; 11.05109026319]
Centroid: CG[12.71442857143; 3.68436342106]
Coordinates of the circumscribed circle: U[14; -2.66994651996]
Coordinates of the inscribed circle: I[11; 4.83547699015]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 148.2498683744° = 148°14'55″ = 0.55441650105 rad
∠ B' = β' = 132.5476665884° = 132°32'48″ = 0.82882169214 rad
∠ C' = γ' = 79.20546503724° = 79°12'17″ = 1.75992107217 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.