# 15 18 28 triangle

### Obtuse scalene triangle.

Sides: a = 15   b = 18   c = 28

Area: T = 121.5466030375
Perimeter: p = 61
Semiperimeter: s = 30.5

Angle ∠ A = α = 28.83773956831° = 28°50'15″ = 0.50333075024 rad
Angle ∠ B = β = 35.36655262339° = 35°21'56″ = 0.61772448745 rad
Angle ∠ C = γ = 115.7977078083° = 115°47'49″ = 2.02110402767 rad

Height: ha = 16.20661373834
Height: hb = 13.50551144861
Height: hc = 8.68218593125

Median: ma = 22.31103115173
Median: mb = 20.57991156273
Median: mc = 8.86600225733

Inradius: r = 3.985511575
Circumradius: R = 15.55496645523

Vertex coordinates: A[28; 0] B[0; 0] C[12.23221428571; 8.68218593125]
Centroid: CG[13.41107142857; 2.89439531042]
Coordinates of the circumscribed circle: U[14; -6.76769836478]
Coordinates of the inscribed circle: I[12.5; 3.985511575]

Exterior(or external, outer) angles of the triangle:
∠ A' = α' = 151.1632604317° = 151°9'45″ = 0.50333075024 rad
∠ B' = β' = 144.6344473766° = 144°38'4″ = 0.61772448745 rad
∠ C' = γ' = 64.2032921917° = 64°12'11″ = 2.02110402767 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.